> The reason I'm asking is that, to the best of my knowledge, there was a period of "white flight", when urban core was basically left to poor people (or at least that's how I interpret this). My understanding is that at the time that was bad. Now rich people "move back in" and I get a vibe from similar articles that this is also bad. So, which is it?

"White flight" is bad for the poor that are left behind in a community with less resources.

"Gentrification" is bad for the poor that are displaced.