https://en.wikipedia.org/wiki/Bowling_Alone
A book published in 2000 based on an essay from 1995. I remember my sister took a university course on it.
The Internet only replaced social interactions for a tiny group of enthusiasts at that point and "phones" were the size of small briefcases and were novelties in cars at that point (1995).
Declining socialization has been happening for _decades_ and people are overly focused on smartphones as a cause.
https://www.fastcompany.com/90653986/traffic-devastates-loca...
As we've become richer, we've bought more cars, we drive them more often, and to further locations. The amount of vehicle traffic and parked cars in neighborhoods have long exceeded the limit for how much you can have before streets become unsafe. This is why children can't go outside unsupervised anymore: there are too many cars, going too fast, and too many parked cars that are too good at hiding children about to run into the road.
You have to get rid of the cars, or limit their use somehow. Eliminate on-street parking. Get rid of monster trucks and SUVs that can only see the ground 22 feet away. More speed bumps and traffic calming.
This really isn't it. People think their kids are going to get murdered/kidnapped/assaulted. "It's 10PM, do you know where your children are?" was a local news promo. You had "news magazine" TV shows designed to frighten parents which were just tragedy porn for attention.
"My kid is going to get hit by a car" isn't why kids don't go out and play any more, it's the news manipulating culture for decades.