That's actually more plausible to me than a bunch of insane architects trying to outcompete each other.
Something would have stopped them: money, safety regulations, sanity regulations, budget of the animators drawing the fucking scene.
But all these concerns fly out the window if we consider Magic.
So, my theory is:
Mami's lived long enough in her apartment it's started warping the laws of reality to appear as a cozy smallish Japanese flat on the surface, but also have infinite rooms for friends to stay over who would never come.
Homura's always rented the same apartment over the timelines, so now it's karmically connected with her by strings of fate and becomes more and more sci-fi with each iteration. She hasn't noticed, because the same reasons as Madoka; the change was gradual and she wasn't paying attention.
Kyouko's father (destitute!) church probably started warping into a big-ass gothic cathedral sometime during her Megucaing.
Madoka's house is a giant fucking upside down chair. Nuff said.
The bigger buildings, like schools, malls, mug shops(?) are the result of all human visitors' Potential coalescing into one distinct theme.
We just need to wait for a while to confirm this theory. If, after a few months ( read decades irl ), Mami's apartment starts coloring itself in iridescent sheens of all hues, becomes detachable from the rest of the building or starts sprouting signs forbidding visitors to leave unhugged or microwave tea inside it, then I can smugly say I told you so.