As a parent, I've noticed the biggest problem that prevents "free range" kids is other adults without kids.
Those of us WITH kids relish getting the kids outside and out of our hair. But those without kids frequently are calling the parents to complain our children are roaming the neighborhood, perhaps on their property. Or they fear these kids will create problems. Usually, however, they're just kids being kids. Going on adventures & learning to resolve their own problems without a grownup hovering over them.
I think the issue is the proportion of adults with kids has declined, so parents run into non-parents all the time that don't enjoy seeing kids roaming around. Whereas when I was a kid, most adults were more understanding.