Cause of problem: Missing Middle Housing. Not everyone needs the concrete beehives or the single-family-home. But there's been very little built in-between in recent decades. https://en.wikipedia.org/wiki/Missing_middle_housing

I could live in very little space. Not into owning a lotta stuff, entertaining crowds. 15x25 is more than enough. Noone's building cottages these days. Let alone on nice streets with trees, away from traffic, walkable. A couple of US cities have opened that up. Neither is in CA. My family of 4 was once quite comfortable in one apt. in a quadplex. We did this to ourselves, and invested in a lot of infrastructure to be locked into.