What you're asking for, an explicit effort to "decommission" small towns, is in some ways also signing the death warrant on a way of life, a culture. I don't think there's a humane way to do thatThe humane save people, not cultures. All the culture in the world isn't worth the suffering of a young working couple who have to live out of their car because of NIMBYism and our continuing efforts to subsidize small towns.
I think there are healthier perspectives available, with recognition that different people have different wants/needs
If more people really wanted to live in small towns, they would be expanding, not contracting. Clearly some people want to live in small towns, but many of these small towns won't be able to pay for their own hospitals and community services at some point. Some small towns will survive - after all, you seem to want to live in one. And no one is stopping you. But you are now a part of a small minority, and we need to have a plan to care for the last of the old people who live in some of these towns as they fade away.
The most unjust thing we could do is ask for young people living happily in their cities to subsidize a 'culture' they have no meaningful connection to or interest in. The real culture is where the people are, and soon that won't be small towns.