I follow the argument but the conclusion feels off. If the reason white collars move in is that it's nicer and more desirable, is the solution not improving a place? Making it worse?

It seems like the solution would be making nice cities less rare, and thus less of a hot commodity, rather than preventing them. After all, nearly anything that would make an area nicer to live in, would also make it more desirable, and therefore less affordable. I can't believe letting inner cities be hideous slums is the best thing for society overall (historically, indeed quite common).