For what it's worth, I'd love to know the answer to this. But I'm not as doubtful as you are, based on the (few) kids I know who do live in more walkable areas

For what it's worth, I'd love to know the answer to this. But I'm not as doubtful as you are, based on the (few) kids I know who do live in more walkable areas where they can see their friends in person without requiring an adult. But your last paragraph seems to be once again missing the "takes as a given ... that the proximate cause of the issue is phone / social media centrism" part. Nobody in this thread has argued against that problem.