NYC is self-described as a "City of Neighbourhoods" (NYC.gov).

Youre not describing anything about pittsburgh that's not true for literally any major city on this planet. Name one homogeneous major/big city.

You'll find the same is true for Philly, LA, all of them. It's perhaps arguable that this is more pronounced for East Coast cities than West Coast because of their historic nature, but it's true for every City. Pittsburgh is unique in a lot of ways, but this isn't one of them.