I think people get fixated on high-density urban construction and miss the impact that is available by simply allowing the next increment of infill in the 80-90% of US urban land that is currently restricted to single family houses on large lots.
If 80% of the housing units in Atlanta suddenly had the option to add a garage apartment, I would expect to see an enormous improvement in the housing market.
Cases like Minneapolis, which basically just made this change, will be important to watch going forward.