They're not unaffordable to everyone. People are renting all those market-rate apartments that get built. The vacancy rate is extremely low.

I already explained how it helps. It preserves more affordable housing by preventing gentrification of existing housing units.

And presumably these new buildings will also increase the affordable housing supply because 25% of the units will have to be set aside for lower income people... that happens with most new developments in NYC. 1/3 of the new units added over the last few decades have been permanently affordable.

Rents are never going to go down until the rate of construction surpasses the rate of population growth... or there's a mass exodus like during COVID. Otherwise our shortage just gets worse every year. And NYC has been growing in population 5x faster than housing supply has grown for the past few decades at least. In that context, new construction can only slow rent increases.