this sounds nice, but neglects the fact that (1) materials cost has gone up and (2) zoning requirements exist. (1) means its just more expensive to build overall, and (2) means that a lot of proposals for apartment complexes get voted down.
Part of building more is getting government (mostly) out of it so that things like zoning laws don't hamper new development. Obviously that is very hard to do at a local level when incumbent homeowners' housing values would be cut in half overnight.
You're not wrong. There are multiple aspects of government involvement that require untangling which includes federally backed mortgages that allow banks to be more lax on loan terms (which is how we got 30 year loans and Trump proposing a 50 year)