What was neat about SF circa 2005-2012 is that folks in general were happy, excited, and proud to be here. Current day tech workers complain a lot, while contributing little (presence, acceptance, consciousness) to help solve anything: viz the comments on this post. Now they dance upon its grave as they decamp to Montana or Ohio, etc. So in a sense part of the problem is just the mood of the place.
If you ever read Jane Jacobs "The Death and Life of Great American Cities" she describes exactly the cycle we are experiencing: a cheap place is colonized by artists and eccentrics, it becomes cool, this attracts mainstream folks, this makes the place hyped & expensive, the people who made it cool move away, it then becomes lame, eventually it decays, is abandoned, and becomes cheap again.
Be zen, this is all part of the normal life of the world. In the fullness of time, SF will have many more boom and bust cycles.
Your argument seems to basically be, once the high-salaried tech workers leave, the city will get worse. But as far as I can tell, the presence of the high-salaried tech workers has been making the city worse over the last decade, and if you think it's anywhere near "a dump," I think a lot of people will be glad to get back the SF of years past (such as the SF of a couple of years before I arrived, before the second startup boom, before modern venture capital existed, before Uber and Airbnb, during the recession and the dot-com bust - the SF about which people like me said, I'd like to move there).