Making it illegal to build new homes for yuppies does not keep older homes affordable. Rich people just buy the old homes and build luxurious new homes inside their walls, which drives up the price of housing. I understand that this is unsatisfying to people who want housing for the neediest first.
I would be very pleased if we could find a way to build brand new 30 year old houses. Unfortunately that is impossible; so the next best thing is to allow rich people to take the depreciation hit on new homes so they don’t buy existing cheaper homes and gut renovate them into new luxury housing.