Go to Manhattan and tell me that housing isn't built because of NIMBYism. It's: RTO (very important!), cost of land (land isn't increasing in volume), end of tax subsidies (programs that gave developers tax breaks), zoning (hey let's demolish all the jazz clubs in Greenwich Village and replace it with affordable housing - is that what you consider the correct line?), jobs (the economics of people moving to a place) and many many many more factors.
About once a week someone with a singular conception of the world of housing comes and you need to open their minds up a bit.
You want to lower housing costs? Maybe increase public transportation, give workers rights to work from home, and invest in expanding the suburbs by making them more dense. But don't do that until AFTER you've established the infrastructure piece. Not everyone wants to live in LA or Austin and spend hours in cars.
If you don't do these things then people all want to live in the same place, which is far more impactful than this "NIMBYism" thing, not everything is your local HOA or little town's regulations.
“hey let's demolish all the jazz clubs in Greenwich Village and replace it with affordable housing”
Or just rebuild them in the commercial space under the new taller condos, so more than just the nepo trust fund babies or lottery rent control people can live in them. These are all non-issues once you get over people’s aesthetic preferences.
This is not just a California issue, the space between downtown and midtown is severely under-built when compared to the economic output of those spaces.