Let's roll the clock back to 2012--Minecraft 1.2.5. The modding scene in Minecraft was booming while Forge made it easier and easier to install mods built against an API to ensure (mostly) compatibility. As it became easier to play with multiple mods installed at once, multiplayer was still a problem in finding ways to easily distribute the mods and config settings to your friends. It's a real headache to try to do this stuff manually as it involves making sure that the same mod versions and config settings are being used between the server and the connecting clients. And mod authors were often DMCA happy about you just bundling this all up in a package and handing it out on the internet.
The Technic team created a launcher which easily bundled all the necessary mods and settings including a ready-to-roll server package which barring permission issues is essentially a drag and drop process through Filezilla and running the launch script. This collection of mods was the first modpack, in a sense. Though true it's debatable since players distributed mods between their friends unofficially, Technic's Tekkit was the first one-click install solution that was easily accessible for thousands of players. This resulted, however, in a lot of friction between mod authors and the Technic team since the mods being downloaded weren't going through adf.ly links or from the author's sites or other venues where they distributed their mod and options to receive a small amount of ad revenue or donations were obscured. It put players in the position of getting their mods through a second party and distanced themselves from the authors. It's hard to say if this has resulted in a better or worse modding community. For the better, many mod authors are using blanket open source licenses and modpack permissions while a few resiliently stand by the ownership of their code and enforce their rights. You could look at authors like Pixelmon and Tropicraft who deliberately make it almost impossible for the common man to include their mods in a modpack. Who actually plays modded Minecraft one mod at a time, though? Why would they make it harder to play and enjoy their mods through multiplayer when at its heart that's really the most fun aspect of the game? It's their right to and their code--they wrote it against the Forge API not vanilla's code, but it's still asinine and backwards. Either way, mods have left an impact on Minecraft that many would agree have been what bolstered its popularity through the years.
The original Tekkit was a complete transformation of Minecraft that focused heavily on industrialization and automation. You could build nuclear reactors to power machines that mined and crafted for you so you don't have to spend hours doing that grindy, pesky mine and craft kinda stuff? Bam--transformation where the end game is far different than the vanilla game. The original Tekkit can still be played through the Technic launcher and is referred to now as Tekkit Classic, and the latest unstable build was actually based on Minecraft 1.5.2. The development of Tekkit Classic, however, has been stopped completely which was the end of something amazing that completely changed the way we play modded Minecraft as easily as we play the vanilla game.
Tekkit Classic has spawned two offshoots--a Tekkit Lite for low end computers based on 1.4.7 (incidentally for being "lite" and for low-end computers, 1.4.7 was one of the few Minecraft versions that didn't have an Optifine release). There's also Tekkit Main--the newest and most modern incarnation of Tekkit based on 1.6.4. It basically keeps the same feel of the original Tekkit focusing on automation and machines, but some mods in it are notably absent like IndustrialCraft and Redpower or don't even work like Equivalent Exchange 3. Why would you put a WIP mod that's not usable in-game in this modpack? Pahimar is a good developer and EE3 will be ready when it's ready, but it's like the Technic team knew they were changing so much in Tekkit it would be nothing short of heresy to not roll out EE3 even if it was technically available for 1.6.4 but not entirely playable.
However, there are mods like Galacticraft and Mystcraft installed which brings a fun new aspect of space mining and mining worlds into the mix, but Mystcraft is like a ticking nuclear bomb on a server that no sane admin would allow his players to indefinitely create new worlds. And I love Thermal Expansion as much as the next person--it's become a lot of people's go-to energy mod while its RF is becoming the de-facto energy source in a lot of mods. But because of Thermal Expansion's ubiquity it's become a staple in almost every modpack and unfortunately makes almost every tech based modpack feel the same. Once you chain a bunch of energy cells, magma crucibles and magmatic dyanmos together you can achieve near-perpetual energy as long as you have enough cobblestone and netherrack to melt down into lava and really--when do we EVER run out of cobblestone and netherrack? And this isn't even end-game tier power production but something you can easily achieve in about two hours of gameplay if you know exactly what you need to build and what materials you need to make them. Atomic Science and Big Reactors is also available in Tekkit but there's really not a lot of incentive for days worth of planning and building to create these machines and look up wikis on how to do it when you can get an efficiency V unbreaking III diamond pickaxe and go to town on the nether and get more netherrack than you'll ever possibly use in 20 daisy-chained magmatic dynamos and 10 hardened energy cells in a five hour session.
In a lot of people's opinions, including my own, Tekkit Main though a fun take on the ideas of automation and industry in Minecraft doesn't entirely live up in comparison to its predecessor in Tekkit Classic. Hell, even Tekkit Lite feels more like the original Tekkit than Main does. It's hard to know if the blame lies in the magic of the original Tekkit being lost after you've already played it or if there's really some parts of Tekkit Main that just don't click with what you've come to expect from this modpack. That's not to say Tekkit Main is bad--it's quite good! It's just not really what I personally expected with the lack of IndustrialCraft and a neutered, unfinished version of Equivalent Exchange. But with using so many mods we already see in a lot of tech packs it doesn't really distinguish itself above the rest the way it used to when it was one of a kind. To be fair, it's not like Tekkit Main is based on these newer packs but that it unintentionally sired hundreds of generic tech packs that can be easily published on the Technic platform, as well as many similar packs being available on the FeedTheBeast and ATLauncher platforms too. You could compare it to YouTube Poop in that sense and our abundance of generic "Imapersonator's" and countless YTP'ers striving to be copies of the poopers they idolize.
I'd say overall it's probably not the Tekkit experience you remember, but that doesn't mean it doesn't have it's own charm. It's still all about the automation, the pipes, the electricity, and the overpowered end-game you work towards. The point to where you open your ME Access Terminal and see materials increasing live as diamonds, jewels, and countless types of blocks are indefinitely pumped into your storage system through your meticulous ingenuity is truest spirit of Tekkit Classic, and Tekkit Main delivers the same satisfying end game experience even if it's mid-game is bland and generic.
The Technic team created a launcher which easily bundled all the necessary mods and settings including a ready-to-roll server package which barring permission issues is essentially a drag and drop process through Filezilla and running the launch script. This collection of mods was the first modpack, in a sense. Though true it's debatable since players distributed mods between their friends unofficially, Technic's Tekkit was the first one-click install solution that was easily accessible for thousands of players. This resulted, however, in a lot of friction between mod authors and the Technic team since the mods being downloaded weren't going through adf.ly links or from the author's sites or other venues where they distributed their mod and options to receive a small amount of ad revenue or donations were obscured. It put players in the position of getting their mods through a second party and distanced themselves from the authors. It's hard to say if this has resulted in a better or worse modding community. For the better, many mod authors are using blanket open source licenses and modpack permissions while a few resiliently stand by the ownership of their code and enforce their rights. You could look at authors like Pixelmon and Tropicraft who deliberately make it almost impossible for the common man to include their mods in a modpack. Who actually plays modded Minecraft one mod at a time, though? Why would they make it harder to play and enjoy their mods through multiplayer when at its heart that's really the most fun aspect of the game? It's their right to and their code--they wrote it against the Forge API not vanilla's code, but it's still asinine and backwards. Either way, mods have left an impact on Minecraft that many would agree have been what bolstered its popularity through the years.
The original Tekkit was a complete transformation of Minecraft that focused heavily on industrialization and automation. You could build nuclear reactors to power machines that mined and crafted for you so you don't have to spend hours doing that grindy, pesky mine and craft kinda stuff? Bam--transformation where the end game is far different than the vanilla game. The original Tekkit can still be played through the Technic launcher and is referred to now as Tekkit Classic, and the latest unstable build was actually based on Minecraft 1.5.2. The development of Tekkit Classic, however, has been stopped completely which was the end of something amazing that completely changed the way we play modded Minecraft as easily as we play the vanilla game.
Tekkit Classic has spawned two offshoots--a Tekkit Lite for low end computers based on 1.4.7 (incidentally for being "lite" and for low-end computers, 1.4.7 was one of the few Minecraft versions that didn't have an Optifine release). There's also Tekkit Main--the newest and most modern incarnation of Tekkit based on 1.6.4. It basically keeps the same feel of the original Tekkit focusing on automation and machines, but some mods in it are notably absent like IndustrialCraft and Redpower or don't even work like Equivalent Exchange 3. Why would you put a WIP mod that's not usable in-game in this modpack? Pahimar is a good developer and EE3 will be ready when it's ready, but it's like the Technic team knew they were changing so much in Tekkit it would be nothing short of heresy to not roll out EE3 even if it was technically available for 1.6.4 but not entirely playable.
However, there are mods like Galacticraft and Mystcraft installed which brings a fun new aspect of space mining and mining worlds into the mix, but Mystcraft is like a ticking nuclear bomb on a server that no sane admin would allow his players to indefinitely create new worlds. And I love Thermal Expansion as much as the next person--it's become a lot of people's go-to energy mod while its RF is becoming the de-facto energy source in a lot of mods. But because of Thermal Expansion's ubiquity it's become a staple in almost every modpack and unfortunately makes almost every tech based modpack feel the same. Once you chain a bunch of energy cells, magma crucibles and magmatic dyanmos together you can achieve near-perpetual energy as long as you have enough cobblestone and netherrack to melt down into lava and really--when do we EVER run out of cobblestone and netherrack? And this isn't even end-game tier power production but something you can easily achieve in about two hours of gameplay if you know exactly what you need to build and what materials you need to make them. Atomic Science and Big Reactors is also available in Tekkit but there's really not a lot of incentive for days worth of planning and building to create these machines and look up wikis on how to do it when you can get an efficiency V unbreaking III diamond pickaxe and go to town on the nether and get more netherrack than you'll ever possibly use in 20 daisy-chained magmatic dynamos and 10 hardened energy cells in a five hour session.
In a lot of people's opinions, including my own, Tekkit Main though a fun take on the ideas of automation and industry in Minecraft doesn't entirely live up in comparison to its predecessor in Tekkit Classic. Hell, even Tekkit Lite feels more like the original Tekkit than Main does. It's hard to know if the blame lies in the magic of the original Tekkit being lost after you've already played it or if there's really some parts of Tekkit Main that just don't click with what you've come to expect from this modpack. That's not to say Tekkit Main is bad--it's quite good! It's just not really what I personally expected with the lack of IndustrialCraft and a neutered, unfinished version of Equivalent Exchange. But with using so many mods we already see in a lot of tech packs it doesn't really distinguish itself above the rest the way it used to when it was one of a kind. To be fair, it's not like Tekkit Main is based on these newer packs but that it unintentionally sired hundreds of generic tech packs that can be easily published on the Technic platform, as well as many similar packs being available on the FeedTheBeast and ATLauncher platforms too. You could compare it to YouTube Poop in that sense and our abundance of generic "Imapersonator's" and countless YTP'ers striving to be copies of the poopers they idolize.
I'd say overall it's probably not the Tekkit experience you remember, but that doesn't mean it doesn't have it's own charm. It's still all about the automation, the pipes, the electricity, and the overpowered end-game you work towards. The point to where you open your ME Access Terminal and see materials increasing live as diamonds, jewels, and countless types of blocks are indefinitely pumped into your storage system through your meticulous ingenuity is truest spirit of Tekkit Classic, and Tekkit Main delivers the same satisfying end game experience even if it's mid-game is bland and generic.