The way to address housing affordability is to build more housing

Except that there’s no such thing as a pure free market. Certain areas are desirable because they’re within walking distance of a subway station, or a commuter train station or are close to the interstate.

Agreed on both counts, but market forces are a powerful tool to use with respect to responding to demand for something.

Right now the market can’t respond to demand for housing except to raise prices.