I think a major change over time has been about vehicles, and there are no relevant mentions of "car" or similar in the article. They're larger, often faster, there are more of them and sightlines are poorer. Drivers potentially on their phones too. As a parent of a 10yo, vehicles are my major concern with out-of-home autonomy.

Growing up in the 80s, we kicked a football on the street and towed each other on skateboards with bikes. I barely remember a car being parked out there; they were all in driveways. That same cul-de-sac now is choked with parked cars that are each household's second or third vehicle and left on the street because it's easier than shuffling cars in a narrow driveway. Now, you couldn't kick a ball without hitting someone's car. A car driving down that street will have terrible sightlines with seeing a kid chasing a ball out onto the street or even seeing someone short trying to cross the road from behind an SUV or 4x4.

Out camping in the bush, I'm comfortable letting my kids roam (as long as they watch out for snakes). Lots of other ways for them to get injured, but no cars. There's a difference between a "learning injury" and the bonnet of a 4x4 hitting their head/neck.