Most buildings in Manhattan are old. Many of them are larger than current zoning would allow. It is very hard to change zoning law, or the political status quo in general, in wealthy neighborhoods in Manhattan— we have accreted a process that makes change very difficult, though not as ridiculous as San Francisco.

Many new buildings in Manhattan are built in central Manhattan neighborhoods where tall buildings are legal. But new buildings built in wealthy areas of lower Manhattan can be smaller than older ones. See this rendering of 300 Lafayette Street, to be built in place of a gas station, and about half as tall as the 1920s building down the street: https://si.wsj.net/public/resources/images/BN-OA513_NYWTD0_P...