I highly recommend playing with a mod pack on a return playthrough. You can still do all of the vanilla stuff, but the experience is also expanded upon with things like steam quarries, programmable mining bots, digitized wireless storage, blood magic, dimensional travel, and cozy kitchens with in-depth cooking.

I used to drive pretty hard into Feed The Beast, but All The Mods seems to have taken over it. The big thing with these packs is making all the mods play nice with each other, so they can share resources and be cross compatible.

I recall one pack where the world was a wasteland. All the ores were depleted, and the oceans were toxic. You had to figure out how to try to grow crops, make survival gear to explore, and eventually make mystical crops that could produce tiny bits of ores that you could harvest.