All you need is one or two of those generations to have more than one kid and the same dynamic that makes it unaffordable for everyone will make it unaffordable for at least one branch of that generational family.
So why can’t FAANG build offices in Detroit? In the Bay Area the lack of affordability comes from concentration of high paying jobs in a small area. They have the economic clout to push the area to build more, or expand in another part of the country.
Actually no, the lack of affordability is 100% due to political decisionmaking that for the past 30+ years has failed to generate enough housing to match population growth. No supply + extreme demand -> massive increase in prices.