A big issue is what we're building rather than how much we're building or what we're converting.

There is way too much ultra-luxury buildings getting built in NYC. It's simply too profitable and there's little to no incentive to build (or convert) apartments normal people can afford.

Another problem for NYC in particular, a lot of the buildings that exist already would be illegal to build now. I get the desire to avoid streets being in constant shadow from surrounding buildings but large footprint buildings are simply a more efficient use of space once you factor in things like elevators, fire escapes and electrical/mechanical ducting.

The NYC government works at the behest of property developers so this is unlikely to change.