I've lived in the Philadelphia area since 1982, part of it in Old City Philadelphia. What I've seen during this time is that large numbers of middle class people and employers have left the city. Many have relocated to the adjacent suburbs. At one time the suburbs were "bedroom" communities from which people commuted into the city to their jobs. The suburbs have become more and more independent of the city, as employment and services have all grown to support the people who live in them. I live 15 miles outside of center city, and I go into the city only a few times per year, and then it's mostly just to drive to the airport. I have no need to go there, and little desire.
It's really very sad. Philadelphia has an inspiring history, and many interesting sites. Unfortunately, it is hurt by high taxes, crime, filth, lack of employment and a bad reputation. The last few times I've gone into the city, I've also found myself uncomfortable with the ever-increasing numbers of women walking around in muslim garb. It gives me the chills.
Yes, Benjamin Franklin, Benjamin Rush et al would be “shocked” at the betrayal of American values there.