I also totally agree that it's mostly the newcomers' barefaced pursuit of wealth and becoming "elite", that's driving this shift. People used to want to move to the bay because that's where UNIX geeks and internet enthusiasts went to find like-minded individuals (after Bell's decline) and get funding. Now it's where the aspiring class goes to join the top 10%, and the goods and services cater to it.
Last time I went back (immediately before the whole COVID situation), my SO and I did a road trip from LA to Sacramento, staying mostly with family along the way. We found San Luis Obispo and the various towns between it and Santa Barbara to be varied and delightful (Los Osos, Solvang, Avila & Shell Beach). Cambria also seemed nice, but we blazed through it. The little communities west a north of Santa Cruz, in the mountains also have a special place in my heart. Next time we're back, I'll try to visit SD.
However, I can't help but notice that all of these towns are smaller and much less of a mixing pot than the greater San Jose area, though. I thought one of the coolest parts of my early life was how it was extremely normal to be surrounded by people of diverse socioeconomic and ethnic backgrounds (I went to a public school), and also how normal it was to dream big (social mobility was all around you). Maybe it's a time and place thing, and it doesn't come together very often.
I caught wind of some tech youtube vlog drama this week and I noticed that the newer generations view FAANG like some viewed Wall St. in the 80’s. The sorting hat for riches changes the gnomish wonder years of the Valley for sure. Also, the open air elitism is just plain tawdry now.
I would say San Diego has the closest look and feel to the South Bay when we grew up. Hard tech in the bio and life sciences provides an educational attainment culture and not so much cash chasing.