Which... is pretty much what he’s saying? If all those who can command a higher wage leave (and don’t return), the local economy becomes hollow and a creeping ghetto sets in.
I read it as more of a "they actually like it better in the rich cities" which many people do not. Specifically the sentence "the people who could left in their teens to major economic centers for tertiary education and considered going back home worse than a death sentence." If a nuke were dropped on SF tomorrow there's a large number of people who would be like "welp, I'm out of a job but this is a perfect opportunity to move back to BFE". The same goes for every major city. There's a reason all (for smaller than average values of "all) the wall street types move either upstate or to Florida once they've become rich enough that they can either let their career coast or retire.
It’s worse than that... whole states are experiencing brain drain. As agriculture continues its consolidation, significant parts of the country are losing anyone who can leave.