> I'd say that this movement of people who can afford it just another side effect of something bigger.
It sort of sounds like you answer your own question (/hypothesis): consolidation of industry. Which also seems to be a pretty big driver in wealth inequality. I've no idea what the correct response is here -- greater regulation to increase competition, so that there are more smaller players across any given industry? Who knows.
There's always the chance that the past is viewed with the optimism of youth of course. There's certainly a difference in social glue in a world where everyone is either self-employed or has a single layer of management above them. Plus, truly local companies are better local citizens (sports teams sponsors, money for charities, build decent and long-lasting buildings).
Dunno what the answer is besides accumulate a financial warchest, live where you like, watch the battle at a distance.
I'm old enough that I remember my home town (which has been inundated by California retirees) as having 100% family-owned grocery stores, drug/general/hardware stores, distributorships, all of which started shifting heavily to chain and corporate dominance by sometime in the late 1970's. Since the modern concept of retiree and tourism based economies hadn't taken hold, towns of that type had to be mostly independent in terms of income for money inflow....small factories, mining, farming and ranching, etc.
I'd say that this movement of people who can afford it just another side effect of something bigger. The irony that a lifestyle of living in a nicer small town with a Powerwall and a Model 3 is both less sustainable and less diverse is not lost on me.