>In Iowa, for example, they are allowing roads to go back to gravel because they lack the resources to maintain the status quo of road infra [7].

A gravel road to a dying town doesn’t seem like a failure mode to me.

They don’t build train lines to dying towns in Europe either.

In my comment, I am using it as signal wrt infra cost affordability. I agree it is not a bad solution as population declines continue where it occurs, versus having no road. Look at infrastructure cost projections to understand if it is within the light cone of economic affordability. If it can't be paid for with a combination of taxes and debt, it isn't possible.