The problem in Detroit was there was no price low enough to get people to live there when there were so many places with similar amenities and better quality of life nearby. In SF, the second housing prices fall, they're scooped up instantly. People move across the country/world to live in SF even when the job market has been terrible in the past. (There's a lot more to SF than a job.) I'm not saying San Francisco could never fall, but we're nowhere near that reality.
I'd say the worst case scenario for SF is probably a city like Philadelphia, which also went through bad years, but has rebounded and has become a pretty great city in many ways, even if it doesn't have the cachet of its past. And I'd imagine that would be the worst case scenario for SF, and the more likely case would be something much better than that, even if all the wealthiest people left SF.
Works for long term planning. In the meantime it won’t be fun for locals.
It is a city that he lost 3/4 of its population, GDP and is still spiraling down.
It has huge abandoned districts. It is hyper-violent.
It has an urban revival that has failed in numbers by population and revenue. But sure, for now it’s “fun”.