That sounds like a worse alternate history, there's no way SF could retain what made it unique if it became 'amongst the largest cities in the world'.
For example, even if only 10% of new residents insisted on driving a car no matter what for daily transportation, due to whatever personal reasons, then that would still be enough to put the city in permanent gridlock all day.
In case anyone is curious, private automobile use went up by 13% from 2019 to 2021 (and by even more since 2017). Driving alone is the most popular form of travel, followed by Uber/Lyft.
Residents don't "insist on driving" in a vacuum. You build the city you want and people move into it. If you don't build car habitats, you won't get cars.
Anyway, SF has desicively destroyed whatever formerly made it unique. The arts community has been extirpated by the housing cost crisis. Even the gay rights activists don't live there any more. The whole city has been hollowed out by Boomers like Cleve Jones who live elsewhere and maintain their vacant pieds-à-terre in prime SF neighborhoods.
Plenty of room. Panhandle upper deck, pave Dolores and GG parks. Bulldoze The Mission and Hayes like the Fillmore was... Plenty of room for flying car landing pads and Manhattanization. Utopia denied.
For example, even if only 10% of new residents insisted on driving a car no matter what for daily transportation, due to whatever personal reasons, then that would still be enough to put the city in permanent gridlock all day.