If you haven’t already, try some modpacks. For extra difficulty, the packs based on GregTech are pretty amazing, like GregTech: New Horizons or Nomifactory. They make it so complicated to produce items that you’re kind of forced to automate things, and then you keep expanding what your automation can do.

GTNH takes like 2 years to build a pair of star gates if you’re playing alone, and they keep making it harder. It’s a massive amount of content.