1. Digging underground is allowed
2. All poi are destructible / buildable
3. (Slightly) random item stats keep me looking for that "best" item.
Now I really like the ship building/tinkering part of Empyrion but their POI (which are few and far in between) will never look as "human real" as the 7D environments because they are tied to a 3m grid.
Yes, they had to balance detail and view distance of bases/ships against performance and something had to give.
It's just harder to feel personally attached to something on the scale of a warehouse and you can never make things look as grunge and lived-in as in 7D.
While Empyrion has "base attacks" it really only means your base gets carpet bombed and you'd better have had enough turrets to win the damage race. There's no planning or strategising involved. Build as many turrets as you can and you either win or you don't.