Here in NJ such mixing is rare; when the cities fell, they fell completely. In some cases barriers like railroads, highways, or bodies of water preserved stretches (much easier to protect, but otherwise all non-blacks (as well as many working blacks) fled.
Those that saw any return of wealth only did so when an area was purged (sections of Jersey City, for instance); nobody was going to sink a dime into areas that could be overrun by disgruntled unassimilated minorities seeking reparations. Asbury Park’s revival stopped almost before it started when the wealthy that had been scheduled to move in realized such a purge would not occur; they weren’t wanted to replace the gibsmedats, but rather to fund them (while they remained just blocks away).
For a long time, Philly really was "the City of Brotherly Love." If you knew were the neighborhoods were, you could sample groceries or restaurants from hundreds of regions around the world, hear different languages and ethnic music. Many of the places of worship had and still have ethnic festivals open to the public with food and music. The big all-City festivals like Fourth of July attracted people from every neighborhood just having a good time. There were always many gay artists in the many cultural venues, long-established gay bars and black jazz clubs where people could find drugs along with great music, and they were quietly tolerated and the general attitude was live and let live. The police were often accused of brutality, but in the 80s, Philly was one of the ten safest large cities in the nation.
But now City Council has even gotten rid of that historic designation — "Brotherly Love" — that originated during the colonial era, presumably because it offends women or because it came from Christian thought.
Now, City Council has designated "gayborhoods", promotes Philly as a gay tourist spot, and has driven the Boy Scouts out of their historic mansion in Center City because it offended gays. Someone upthread mentioned the placement of Section 8 people in the upscale areas. Churches are eviscerated because no one tithes any more — the government is supposed to take care of liberals and the poor! Kenny Gamble the music producer has built a huge mosque and no-go-zone in the urban area just abutting Center City. City Council let in gambling on the riverfront. Why not just open the prisons and let them all out? I go there to visit friends once or twice a year, but even after having lived there for decades, I could never go back.