I've had quite some modded worlds and playthroughs, but the mod that always resonated with me the most was botania.
The way it sells itself as a plant magic mod, while being an automation tech mod at heart (but still requiring tinkering with redstone) is just lovely. It brought interesting ideas into the world, and the way you generate, manipulate and use these pools of mana (while also avoiding GUIs as much as possible) has always been so enchanting and fun to me. :D
It even contains a storage system (craftable once you visited the end), which is unlike any other centralized/universal storage system I've seen in other mods.