> the atomization of intra-family bonds that seems so immoral to you is actually caused by the migration, driven by underlying economic opportunities and not some NIMBY anti-growth mindset

The point is that we have to make a trade-off between free internal migration and NIMBY. If you mix those two ideas together, you get misery. In deciding which is worth prioritizing, perhaps you should consider that free internal migration is a literal bedrock principle of the American state, dating back prior to the Constitution, enshrined legally in the Constitution, on which huge quantities of American legal and economic life have been built for the last 250 years, whereas NIMBY is an ad-hoc political coalition of wealthy homeowners and crotchety neighborhood activists who'd rather no one new get to live in their city.