You don't need to replace historic Victorian and Edwardian houses necessarily, although its one option. Instead you can extend zoning in areas like SOMA to allow much larger buildings there where there aren't as many people already living there and most of the structures aren't nice historic houses. This is exactly what they've done. San Francisco has a whole area of very tall residential skyscrapers in various stages of completion as well as the tallest building on the west coast (the Salesforce Tower) as part of a new transit hub.

Many of the schools are great. Sorry if your school district is bad. There are excellent schools in many areas. Cupertino, most of the Peninsula, Berkeley have some really great ones.

My coworkers for a decade took public transit more often than not. You live in the suburbs if you think 5% of the population takes BART or Muni to work. Plus many people walk or bike.

I've walked all over San Francisco so if you don't find it walkable its on you. Grab an electric scooter, a bike share, an electric skateboard, some rollerblades, or one of those uniwheel things and the hills won't be so bad if you can't handle walking them. The Mission has more streets of great walkability with restaurants and small businesses everywhere than almost anywhere in America.

Perhaps the fact that you don't even know about the BART expansion should be the warning sign that you don't really follow Bay Area transit very closely. Ironic that you ask if I have ever actually lived in San Francisco. Yes I have. Trying to act like the government is so incompetent that they can't open a station when they just opened Milpitas and Berryessa/North San Jose stations on June 13 says more about your lack of attention to local issues than it does about their urban planning. They also built 7,000 nearby housing units. Its actual transit-first development as they've been doing in SF for years.

I've met more people in junior roles get rich in the Bay Area from equity than would ever be possible by trying to live in the cheapest possible place with minimal opportunities such that your expenses are a slightly lower percentage of your take-home pay as a new graduate. If you did an entry level job at Twilio you're probably a millionaire now. People get promoted significantly faster in the Bay Area due to the number of fast growing companies and the pay, which started out higher, grows that much more every year due to promotions, larger cost of living increases, etc.

So sure make your money and leave. Don't try to improve things you don't like, just complain about them. Go somewhere new and find out all the issues there that you didn't realize including several of the ones I brought up here. Learn what a truly unwalkable place is like.