I think there could be a middle ground: rent control that allows increases that average what the free market would follow (this can be determined by looking at how rent is changing in non-rent-controlled apartments), or even a few percent higher than that. This will stop landlords from doing vicious increases, but also will prevent renters from acquiring absurdly low rents.

That would certainly be an improvement. Right now SF allows 60% of CPI, so less than inflation.

The state-wide rent control allows CPI + 5% or 10%, whichever is lower, which doesn’t seem like much of a limit.

Just increasing it to CPI in SF seems like an improvement. Even pensioners get CPI adjustments.