AI dungeon is the shit. I trained a few games to be very much identical to the S.T.A.L.K.E.R. universe, incorporating elements from both the games and the books. The best part about it is that you can always modge it in the desired direction, either by rewriting its prompts or doing something that essentially negates or ignores them.

Doubt we'll see anything worthwhile like that in any 3D capacity, though, as there's much more limitations there - primarily the corporate KPIs