Solving it requires relocation. There's no getting around it because the total cost of living is incompatible with people with slimmer means.
This is a misrepresentation of SF rent control. Rent increases for pre-1979 apartments are only capped if the same tenant lives there continuously -- when the apartment lease turns over, the rent can be raised to market rates.
That being said, there are some people that abuse the system by keeping a lease for a place they haven't lived in for 20 years and subletting it, sometimes for a profit, but there aren't apartments where the rent is permanently capped at 80s levels like you're suggesting.
Smart landlords will fight adding a cotenant, but tenants can always claim discrimination which is an uphill battle for the landlord especially in SF where juries are notoriously anti-landlord.
There's no issues around discrimination for this, and it's not an uphill battle. Replacement tenants are not co-tenants, and do not have rent control protection if the original tenants move out. Landlords cannot reject replacement tenants in most cases, but they have no requirements on accepting replacements as co-tenants. Replacement tenants are added as sub-letters of the original tenant.
I was a real estate agent who worked in property management, and I've also lived in rent controlled apartments in SF. You're absolutely wrong here.
Rent control: A random windfall for whatever tenant snags these coveted apartments when someone dies in a 3 bedroom apartment they haven't needed in 30 years but "can't afford" to downsize from since they have been paying $650 since 1989. Also the illegal subletters who are numerous and shameless, from personal experience.
Low-income housing minimums: A random windfall for a few lucky lottery winners, while everyone else from indigent to middle-class has to struggle because the developers need to build only luxury housing to make up for eating the cost of the low income housing.
And then this housing first thing is more of the same.
> siphoned off into these non-profits
Indeed. The homeless-industrial complex of nonprofits in SF is huge, but popular since it is a jobs program for all the people with social science bachelors and masters degrees, and no marketable skills.