Well, you might be right. It does all depend on circumstances, what you've got set up for you, what you like to do on a regular basis, etc.. I just think it's not beneficial to be more isolated physically, and there's other places and ways to improve that.
If I were forced to move back home to the city of ~700k, I'd simply only select a few of the neighborhoods where I'd be likely to bump into people, or get to chatting with someone at the gym or whatever. Making new friends is still hard and takes work and luck, but positioning yourself to make that hard process more enjoyable is something I think a lot of people can benefit from.
Williamsburg and Silicon Valley are extremes of particular personalities and age groups I'd think, but even within that you're going to have some people who are roughly a similar older age with similar interests.
Edit: I'd expand on this idea a little. Making and keeping friends is hard, and is the result of circumstance, discovery. Some things help.
A frequent interval of being around some of the same people for some time increases the likelihood you'll get to recognize them and discover if you have chemistry or any piece of common group. That's why work is most people's default, but it's a dangerous default.
School is a better model, you're paying to be there and there's plenty to talk about.
When I visit friends in the suburbs, it's always fine, I'm happy to see them, but it's very much a druve to and from or transit to and from kind of thing. Some people like that, they like that, but it's not as much my vibe.
Moving somewhere medium dense and walkable, in your own small town or otherwise, won't necessarily mean your life blows up for the good or bad, but it has the potential to change your opportunities, or those of your kids, in my opinion.