Building on that I’ve noticed that there just are an awful lot of ascension perks which (somewhat generally) fit the theme of “improving” your portion of space, whether by giving you better planets (e.g., Mastery of Nature or Arcology Project) or improving your ability to make great constructions (e.g. Voidborne or Galactic Wonders). The overall effect is rather a bit much, especially since these perks vary from the bad (Detox) to the essential (Arcology Project).
A thought I had for improving these was to basically turn them into a second tier of “ascension,” functioning similarly to the existing ascension paths. You would take one of two specific ascension perks (I suggest World Shaper and Master Builders) that focuses you into a Situation and eventually tradition tree that determines how you approach the problem of making the most of the space you control. Will you take your existing planets and mold them into perfect paradises? Cover them with steel and concrete? Or leave them behind for habitats and megastructures?
Obviously this would need to come with a rebalancing that makes gaia worlds (or non-gaia worlds favored by your species, e.g. Ocean worlds for Aquatic species), ecumenopoli, habitats, and megastructures roughly equally balanced at least in the case where you build for them. It might also come with larger changes to terraforming to make it more interesting, for example by making the terraforming process for all empires more similar to that for current Idyllic Bloom or Relentless Industrialist empires. This could also have a lot of interesting interactions with existing origins and civics like the aforementioned Idyllic Bloom or Void Dwellers that could function like some origins and civics that lock you into a particular ascension tree (or even block you from taking an ascension tree altogether) currently.