> 2019 law they passed limits the amount a unit can have its rent increased in the case of a capital improvement at a small fraction of the capital cost

Source? This sounds like it only applies to stabilised apartments.

> Now that interest rates are higher land lords are forced to keep units vacant

Rental vacancies are similar to what they were in 2019 [1].

[1] https://fred.stlouisfed.org/series/NYRVAC