The magnitude of Prop 13's distortions contribute much more to the problem than policies that a city could implement itself.

Housing is often viewed as a San Francisco problem, but really it's an area-wide problem acutely and a state-wide problem more broadly. I.e., areas outside the policy of San Francisco, such as peninsula, south bay, etc, are not significantly cheaper. And entire other metros, like Los Angeles and San Diego, have had similar percentage cost increases (and those metros are actually more "unaffordable" since incomes are lower there).