I think step one is universal healthcare. For many reasons that we all are familiar with by now. (being tied to a job that has income limitations because you need the healthcare(ish) it provides, becoming bankrupted by healthcare costs, getting kicked out of your housing due to medical costs)

The revolutionary silver bullet to begin increasing housing availability is to eliminate the ability to depreciate assets via the tax code if they are single family detached homes. Many of these rentals are already fully depreciated and will remain rentals. But recently purchased (within 10 yrs.) rentals will likely be sold and importantly they will not be purchased by 'investors'. That shift will provide a flood of homes into the market which will apply downward pressure on prices. More people being able to afford to purchase those homes will free up rental availability, thus applying downward pressure on rental affordability.

Now that only addresses single family homes; there remains multifamily housing to be addressed which will be more complex. A robust government regulatory agency for housing is not something we currently have in the usa, obviously. (see picture) Reforms of those regulatory bodies are needed whereby penalties they assess would have actual teeth. I imagine penalties that remove ownership. I also imagine the countless tax incentives used in constructing and rehabilitating these structures being negotiated quite differently, to include public ownership.

Just a few thoughts here; I haven't all the answers. I'm curious when the last housing project was built in the usa.