Most of my playtime in Factorio is with overhaul mods, there's a lot of quality content there. I'm not sure how many of them have been brought to 2.0 or even will be. I'm curious where you think quality lacks.
Space Exploration has been my favorite, but Ultracube, Krastorio2, and Nullius were all quite fun. I'll admit I haven't finished Ultracube and Nullius, but I have restarted my Ultracube run in 2.0.
> Space age is interesting because new planets are being added by fans, but I don't think they're going to be as well designed and really bring anything interesting.
Check out Maraxsis and/or Cerys, these were the kinds of planet mods I was hoping for in Space Age. Maraxsis is an ocean planet and you build underwater and in deep trenches, and the planet's building has a base 50% quality. Cerys is a moon of Fulgora that's really quite small and it's more of a puzzle than anything.