Masterpiece of Possibility

Objectively, it's probably the best Minecraft mod ever made. Create is so polished and expansive that it's arguably capable of delivering as much content as the vanilla game, while maintaining a consistent and impressively high standard of quality.
What sets Create apart from other mods is how basic tools and components interact in exceedingly intricate and fascinating ways. Vanilla Minecraft is an exercise in this philosophy: redstone is wonderful in its simplicity and simultaneously absurd in its depth. Pistons move blocks, Hoppers move items, Redstone Lamps turn on and off. Despite Minecraft's commitment to having fundamental constituent parts that anyone can understand, redstone can be leveraged to build anything from a door that opens automatically to a computer that can run Minecraft inside of Minecraft.
Create feels like taking this same design concept to its logical conclusion. Rarely does a block or item in Create perform a complex function all by itself; instead of a magic machine which produces Cobblestone and automatically outputs it to a neighboring inventory, Create has drills for breaking the blocks and novel ways to move items around and flexible filtration systems for ensuring your Cobblestone goes where you need it to. There is sincere thought put into how each available tool can be used in myriad ways, and how those tools interact in an exponential explosion of possibility. That is the key word which defines this mod: Possibility. It's all well and good that Create is exceptionally-made, with beautiful textures and a genius in-game documentation system in the form of Ponder, but it is also enormously interesting in that rare way where the possibility space is so large that imagination genuinely is the limit.
This is a point which is unfortunately missed in many of Create's derivatives. Many add-ons to the mod are antithetical to its design; they give solutions rather than tools. Create is frequently overshadowed by simpler mods which combine its multi-step contraptions into single blocks. Due to its popularity (and, being honest, its near-incomparable quality), many large contemporary modpacks include Create without giving it the treatment it is asking for, leading to players blitzing through the "progression" of the mod when that is not the primary purpose around which it is constructed. It is surprisingly feature-complete on its own, and it's difficult to get bored of innovation. Install just Create and let your ingenuity run wild, and see if you can't make something unique.