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I don't wanna by Richard Mozzarella, on Flickr

Do you not see the contradiction between a dense vibrant walkable city that is diverse, interesting, full of opportunity & wealth and the hollowed out ghost town you are scared it could become? A building occupied is never vacant. It can never be blight. That is key. Mult-use buildings easily configured to whatever use or mix of uses appropriate to that time and place. Shops, manufacturing, grocery, tailors, bakeries, appliance or furniture sales, etc...on the ground floor put business ventures both within reach of residents but within reach of proprietors to take a gamble on the future. While residential in the floors above provides a steady stream of foot traffic to see the proprietors wares. Free-market capitalism works better.

If you are taking most American towns that can barely support a Dollar General as the soul sign of any economic activity at all as your inspiration...I don't know what to tell you except Main Street was bull-dozed for the car and whatever model that town was built on was shucked out the window long ago in favor of the least density as possible and no services rendered from single use buildings with onerous parking requirements depriving the land owner of the freedom to build out his land in the most effective way possible. They followed the opposite model of the 15 minute city.

A single use Chik-fil-a can only be a Chick-fil-a and will only be so for about 15 years while only supplying fraction of the taxes to the city as the 1920's multi-use building it replaced. And the car dependent nature of far-flung residents trying to get to that temporary single-use building ensures that the cost of maintaining those roads will weigh very heavy on the towns balance books. That's poor planning if the city even had a plan at all.

Roads and houses do not create economic output but they do have a very high cost. It's no wonder people leave as soon as they are able for greener pastures. Their town is bankrupt or eventually becomes bankrupt and unable to keep up with the cost of running a town and the personal cost of living there is too high.

Many people consider being near amenities, services, opportunity to be in their rational best self interest. The concept of the 15 minute city in urban planning arrived organically from this realization.

Do you have any examples of any cities that were walled off and isolated? Is there one example of a town in say Kansas or wherever with a McDonalds & a Wal-mart that "They" walled in and held the voting tax-payers captive? How many miles of fencing is that?