So this is interesting and I agree with most of it, but I honestly still don't think it fixes the affordability problem.
It might help. At the moment more than a few cities out that way are throwing up apartments like the world is ending. It's gonna be like putting paper towels on a bullet wound, but it's something.
But the issue is still demand, demand, demand.
SF might have spent all that time fighting against more density. And yet, SF is very, very, very dense. It is not lacking for density. It is not a city of big lawns, big lots, big houses. And yet, being super dense doesn't at all correlate with having affordable housing.
Until you have people say "enough," stop paying and just leave, all the damn density in the world won't produce anything affordable.
Again, I think of this as being the entire Bay Area, and SF is only one bit of it.
SF is naturally small physically. I.e. if you look at this: https://en.wikipedia.org/wiki/List_of_United_States_cities_by_population_density
San Francisco proper is the second most dense city to New York City, at about 2/3 of the density per square mile. But NYC houses 8M people while SF houses 800K because NYC is physically larger. So you have a completely different order of magnitude in scale between the two.
Where it gets REALLY interesting is if you filter and sort that list of the top 125 incorporated areas based upon metropolitan area.
The New York City Metropolitan area has another 56 incorporated cities on that list which house an additional 2.3M people.
The San Francisco Metropolitan area has another 5 incorporated cities on this list which house an additional 295K people. That's Daly City, San Pablo, East Palo Alto, Berkeley and Albany. Again, that's another order of magnitude. And the highest on that list is 49th in density. 23 of the NYC metro areas are above 49th on the list and are about 1.1M of the 2.3M from that NYC metro.
So yes, San Francisco is expensive, and relatively dense. Even if it reached NYC's density, the population would only go from about 800K to about 1.2M. So it would still be expensive. But if
the entire Bay Area, including extending down the peninsula and across the Bay, was a little more like the NYC metro area, the ENTIRE Bay Area would still have high demand but the affordability point would be much more accessible than it is today.