I was born in San Francisco (so was my Dad, my Mom was born in Oakland and so were her parents etc.) and my family has been through many ups and downs in the Bay Area over many generations. SF used to actually be a cheaper place to live than a lot of parts of Los Angeles. There is no way it will be Detroit though. It's just too desirable of a place to live.

Don't underestimate the possibility of a death spiral. It's already happened once. Read Gray Brechin's excellent book Imperial San Francisco. SF used to be the undisputed capital of the entire North American West Coast, and arguably even the entire Pacific. In the aftermath of the 1906 earthquake, it lost that position to LA.

I lived in SF for 19 years, moved to London (family reasons, elderly parents with health issues) and are planning to return to the US. My wife put an absolute veto on returning to SF itself because of how dire the law and order situation has become.

Sad to say, but the city really needs a 1990s vintage Rudy Giuliani to clean house. Otherwise what it will get is Bernie Goetz (yes, I know, I am showing my age with my references). It seems unthinkable today, but in the 1950s and 60s SF was actually a fairly right-wing city, all mayors from 1912 to 1964 were Republicans.

1912-1964 Republicans may not have been particularly right wing.

My understanding is that prior to the "Southern Strategy" (https://en.wikipedia.org/wiki/Southern_strategy) of the 1960s, the Democratic Party was largely right wing, and the Republican Party was largely left wing.

So San Francisco flipping from Republican to Democrat aligns pretty much squarely with the change in politics of the parties due to the Southern Strategy.

This implies that in fact, San Francisco has always been fairly left-wing.