A significant portion of the population can’t save up for a 20% downpayment in good times, I doubt it’s a realistic expectation for many. The whole thing keeps churning because of FHA (taxpayer funded) lending.

True, but we are talking about a single person, not the population at large. You can personally change your behavior and save up a 20% down payment. You can probably save to a 100% down payment - if the market collapses at the right time (unlikely) in 10 years of living cheaply. Of course you forgo a lot of other things: I personally would rather have the toys now vs a paid for house in 10 years. YMMV, your goals are not mine. If you want to tour the world on a 6 star cruise ship for 30 years staring at age 50, you can save up enough money to do that if you live cheaply enough from age 20 on. (I can't help you live that long though, average lifespan is just under 80, and you could die in an accident at age 49.5 just before you retire)