This NYT bit about zoning was, of course, catnip to me. The big point is that even in cities, the amount of land zoned explicitly or effectively for nothing other than single family detached housing is immense. "Downzoning" has long been a thing, meaning even currently dense areas contain a lot of noncomforming properties. You can knock down a multifamily unit to build a single family home, but you can't do the reverse.
And the inner ring suburbs are generally even worse (Obviously this is a big country and not all cities are the same so generalizations are necessary. "Inner ring suburbs" are more of an older city thing, as those cities stopped annexing their streetcar suburbs.) They tend to be a bit denser, too, but with as much or more of a tendency towards downzoning. Not a lot of new housing of any type being built. Then you get the actual suburbs which tend to be locked in amber, at least residentially, once they are somewhat built out.
That leaves building on the fringes, which happened during the glorious aughts, but the fringes (exurbs) are suburbs of suburbs, and detached from things like cultural institutions, employment centers, and civilization generally. They can be close to nature, which is an amenity, but they're not exactly rural or small towny, just big box stores and strip malls and a very long way from the baseball stadium.
So where do we put the people? Often people want to say "declining rust belt cities" or similar. And, ok, sure, but declining places have declining housing stocks and no jobs. That's why they're declining. And the same policies (or worse) than the more booming places.
