Parents have stuff to do and also nothing to do on playground. So they stop taking kids there once those are over toddler age and won't destroy house put of sheer energy. Playgrouds are boring and 9-11 years old truly have nothing to do there without friends group.
So 6-10 years old kids are rarely outside. They know how to have fun at home and school, but they have no community in park and don't know games. Then they are 14-16 and everyone is like "why don't they go outside? there is basketball court". But shooting balls alone is fun for like two days and they don't known to have fun there.
That's because social media is deliberately designed to be addictive. Zuckerberg et al know this, but don't care, because all they care about is their proftis.
However, there were a plethora of parks, ponds, baseball and basketball courts, skateboarding parks, and an ice rink nearby that were somewhat walkable.
Yeah I spent a little too much time on the computer but I did have a social life and went outside a lot doing all kinds of fun.
I think you are underestimating how much fun kids can have with not very much. I agree that we have serious cultural problems but I think urban planning is the wrong culprit here.
I think at least some of it is lazy parenting who are content with just giving their kids an iPad or throwing them in front of the TV for entertainment.
You know what my sister did with her friends for “fun”? They wrote and acted out plays. This wasn’t that long ago, it was in the 90s.