Wow. Good question!
You know, you just work with what you have. My table is usually a mix of resin sci-fi buildings, paper-craft, and scratch-built stuff.
If you have a 3d printer THESE (and related products) can (eventually) fill up a nice table.
Papercraft can look great if you don’t mind putting a little work into it.
I like to scatter these around to make a neighborhood look kind of rough:
Beyond that, you’re looking at gluing together and painting up foamcore buildings, but that’s a whole topic unto itself.
BLARGH: Red Player One