Delco is where all the white flight from West CoP landed, right?
It depends on the neighborhood. Delco was populated well before white flight was a thing. There were a lot of immigrants, particularly Irish, that came directly to parts of Delco. For example, Havertown and Drexel Hill each had textile/fabric mills that were opened by Irish-born brothers (or cousins, I forget) named Charles and Denis Kelly in the early 1800s. They were major mills and the owners became really wealthy. They recruited laborers from Ireland and towns were built around the mills.
Charles Kelly had the mill in Drexel Hill and the Kellyville section was named for him. It is a working class area and always was. The local Catholic church, St. Charles, was built by him and a parish school was opened to educate the children of the Irish mill workers. The school closed a few years ago.
Denis Kelly opened St. Denis by his mill in Havertown. Similar situation.
More recently, there have been a lot of people moving from Philadelphia. Some was white flight but not any more so than other counties, most likely. Now, you have white flight from Delco.
The biggest change has been the increase in minorities, especially blacks. Most have relocated from blighted sections of Philadelphia looking for better schools and better, safer lives for their kids. There are towns that are still 95% + white but there are historically white areas that are primarily (even overwhelmingly) black. I am not a racist but I am honest. A lot of the areas that have become black have seriously declined. Part of it is the poverty and some is cultural. The biggest reason, though, in my opinion is white flight. People saw a few black families move in and ran for the hills. The house prices dropped with a flooded market and more blacks moved in to fill the void. . . and so on and so on. Ignorance has killed a lot of neighborhoods. A lot of the white people left behind were those that couldn't afford to move away so you see a trashy element. It is similar to Kensington, just less pronounced.
The poor towns in Delco seem to be mostly black. The middle-income areas are proportionately mixed. The upper-income areas are still really white. This is the way things are in most urban places in the U.S. White people will say it is because the blacks moved in. I disagree. If people had just gone ahead and lived their lives accepting their new neighbors, the neighborhoods would have been fine. The flight hurt the real estate market and started a shift toward lower income residents. The problems in these areas are pretty typical of lower-income areas elsewhere, regardless of race.