> it’s not at all obvious that a single median income should be able to support a 4-person family in a 2BR apartment or else the system is completely broken

Either the Western world allows people the financial and real estate resources to have children in the next 5 years or we're all fucked. The tail end of the boomers enters retirement in 10 years and while millennials can take care of the boomers, eventually we will need to be taken care of, and for that millennials need to have children now as long as we still can.