Yeah, but it's not like you can have a general aesthetic or different tone than using a real life city. Plenty of movies that use New York as a setting that have completely different tones and aesthetics to one another.
And for every Gotham that sometimes tries to approach feeling like a real city, you get "totally worse than Gotham" Bloodhaven.
Yeah, I guess I'd say Gotham and Metropolis are grandfather clauses but I don't see how much Superman media would really change if it Metropolis was just changed to New York City in the dialogue.