The issue is that pay hasn't kept up with productivity. As things become more efficient employers are having to pay far less for the same amount of work.

It has in tech - in fact I’d wager approximately 100% of productivity gains since the 80s have been in the tech sector which in turn has probably captured nearly all of those gains for itself.

Job hour and insurance lack of fungibility also make it hard even if you were willing to accept lesser pay it would be harder to find an employer who accepts it. Self-employment doesn't lend itself to fixed smooth workweeks and leaves one uninsulated from all of the demands of running a business.

People stopped borrowing money. Either because they became old or the financial crisis made them risk averse. This drops interest rates.

The few things that people buy with debt then rises in value. There is also no interest in building more housing because that would result in lower single family home property values.

You have to consider that it's the bank that is paying for the house. As the owner you only pay the mortgage, whose monthly payments are limited by how much people can afford in the first place.

There is interest in building housing by home builders, but it's at the expensive end of the market, not the much more affordable housing that we need.

Property value is the biggest component of home prices in many desirable areas. Increasing current low-density home building won't change that, but increasing density would help with affordability. Problem is that many in the US still have low density housing as their housing goal.