I thought this article would be about other things judging from the title, but these are good points.
I'm not that old, and I remember "be home before dark" when I was in the single digits. I was going outside, by myself, since about the age of 5. As soon as I could ride a bike that was it. Basically my parents made dinner and paid the rent, the rest was all me in my own life.
There was a phase in my childhood where I was actually in a very dangerous environment, and as a result my freedom was restricted. I can compare the two. I think it damaged me quite a bit. I wonder about kids who never knew the freedom to be human beings.
Again as a teenager I experienced that freedom and the good fitness that comes with having a wide range and only feet to get around. And there was trouble (exposure to drugs, etc). But all in all the trouble didn't affect me negatively in the long term, I think it was less harmful than if I'd otherwise been restricted, and most adults don't avoid those sorts of troubles either way.
There is a network effect reinforcing this trend. Kids don't go outside because there's no kids outside. Also I think that while the fear of abduction or a terrible accident is there, I think we downplay other factors in the trend now, particularly the increased demand for creature comforts over the last 2 decades (and longer, but more pronounced more recently) and the availability of stimulation indoors. I remember the middle of the summer and going outside every day not once thinking it was too hot to go outside, then spending the entire day out there. People think I'm weird now for not using the AC in my car. I remember waking up in the morning and there was no inkling to check a phone. People can be immensely stimulated laying in bed now, with phones and videogames and such, and there are positives that come with these new tools but there are negative changes as well, and many people are beginning to come to the conclusion that the negatives outweigh the positives.