As someone who has actually managed to work remotely in a small city while employed by a major tech firm at normal pay rates, I can definitely say your scenario does not match my lived experience.
1) unless you move to a very small town, there are still plenty of people in your economic demographic. In the US, roughly 5% of households earn more than $200k. In a town of 70k, you’d expect there to be roughly 27k households and therefore 1300 households earning more than $200k. If you are currently making more then $500k you might be a little more out there, but then you really have no reason to move, do you? (Your techie peers at other companies don’t make that sort of money).
2) “Friends from work” don’t go away when working remotely. We still have “water cooler” conversations and members of my team have occasionally visited each other’s cities outside of work. We also do a ton of socializing when we are physically together for work.
That being said, it does reduce that aspect of social life. What fills it? Other activities- family/children, hobbies, causes, clubs, etc. I’ve lived in major tech hubs before- it did take longer to establish a social network while working remotely in my smaller city, but once established it has been much more fulfilling.
3) I apologize for criticizing, but your concern about not being able to socialize with the middle class sounds bizarre. Some of our dearest friends in this city are solidly middle class- 911 dispatchers, teachers, carpenters, nurses, and sales people. We met through sports, children’s school, and volunteering. We specifically chose to live well below our means (FIREing before the term existed I guess) so our neighbors are a varied lot, and we like them. We can’t invite them to join us vacationing in Europe, but other than that it’s there is little awkwardness.