Can you answer your own questions in reverse? Why aren't new developments built wholesale, complete with shopping and services somewhere out of the way (and cheap)?
Ideas are already being tried. They are also not solving the (entire) problem. But to suggest "just" doing this one thing is a solution to the (entire) problem is easy to say, but how much does it contribute to actually solving things?
(Notably, me discussing this on the internet isn't a solution. It's just entertainment, and hopefully I learn something along the way!)
There are reasons housing prices in expensive areas are what they are. Some of it is poor zoning and land usage that suppresses supply, but a lot of it is also demand. People want to live in dense, vibrant areas, even if they could live cheaper elsewhere.
How are you supposed to predict what to build before anyone moves in? A grocery store is easy, but the hipster main streets that people love are hard to nail down. What stores are going to seem “eclectic” and “cute” to the people who move in, without being too far out there or too “corporate”?
How many bars? What kind of bars? Is the coffee shop fine or does it need some kind of fancy tea time place?
What price point should these places target?
All of this is very hard to know without having people living in the houses who can be polled or observed to see what they’d want.
Cities benefit from high urban density, and reducing density means less benefit.
Cities used to be where young folks found a job and a mate. The job part isn't such a thing anymore due to remote work but I can still see the appeal of a place like NYC if you're trying to find someone.
Also, if by bumblefuck nowhere you mean places like Santa Ynez instead of San Francisco, then yes please.
The digital elite are mostly staying in concentrated areas, they have the money to and concentration leads to much more amenities nearby.
California Forever is trying your thing and facing massive headwinds.