Cities: Skylines 2 is a particularly rough pick for this concept, since it's one of very few games I need frame generation to run even passably. LLMs seem plenty capable of tweaking existing assets to make a ton of variants, but actually displaying all of those performantly is then an engineering problem.

And without many variants, things like "splotchy wall apartment building" would get old so much faster when there's several square blocks of them instead of bizarrely pristine ones.