You also made comments about the crime, traffic and air quality (I have never heard much on that either way) and home prices which do not seem to line up with any actual online stats. If you want to move to a lower cost of living area for retirement that is certainly a choice many retirees make. But if you like the Bay Area there are much less expensive, livable cities outside the South Bay and they aren't all more congested and crime ridden. Traffic isn't a problem in many areas, especially if you are retired and not driving during commute hours heading into SV or SF in the morning or outward bound at night. Concord is on Condé Nast Traveler's top 10 retirement places in the world, in part because it has the amenities of the Bay Area but is lower cost and is on the BART line.
Your home prices are from May, include condo prices, and include counties like Napa, Solano and Sonoma, which I really don't consider part of the Bay Area. All those lists of places to live such as the one you cite are made up by people that have never been to most of them, pick a bunch of statistics, and write an article based on them. Pretty much worthless.
Concord and Pleasant Hill started out as low cost, working class communities. The populations have changed a bit, but they still are not places I would choose to live. An easy way to get a feel for the area is to look at the retail on Google maps. There is a Trader Joe's in Concord, and a tired mall in Pleasant Hill, but not much high end shopping in either city. Where are Nordstrom's and Whole Foods? Walnut Creek.
No disagreement that the corridor from Walnut Creek to San Ramon is a nice place to live. Compare the Costco in San Ramon to the one in Concord. Look at who is in the parking lots and what is sold in the stores. That's a lot more informative than Conde Naste.
I still would not choose to live there because of access in and out of the area and proximity by car to airports, the beach cities, and other amenities. Traffic on 680, especially at the 24 and 580 interchanges, is as bad time wise as it is down here. Commute traffic from the Central Valley clogs 580 and 680.
I won't argue with you about the air pollution. Given the prevailing wind, a lot of it ends up in the South Bay and some days are unpleasant. However, it's not anywhere near as bad as the Los Angeles area, where I find it hard to breathe on a typical day. And the winds that push the pollution south often suffice to clean out the entire Bay Area.
The crime down here is different, much of it gang related or property related. Stay out of the the bad neighborhoods in South Central and East San Jose, and you will be largely immune. Looking at Google maps, the retail has followed the money and supports my belief that most parts of the South Bay are good places to live. The quality and density of medical services is also excellent.
Would I move to the South Bay specifically to retire? No, the cost of living and congestion are big negatives. But my one story house on a big lot was bought almost 30 years ago, I have access to quality medical care, and it's an easy drive to the retail and services I want and need. I'm staying put for now.