(1) Kids are different. What is good for one may be terrible for another. A schedule that an extrovert craves might demolish an introvert. A kid who comes up with tons of intellectual and artistic projects on her own, and wants to lead friends or cooperate with friends in pretend play and other games at her house may thrive, in every way, getting to do just this. I suppose it's possible that some kids aren't as naturally creative and would need a nudge from more structured activities (although I wonder if maybe some of these kids have just never had the chance). And certainly there are activities that require large numbers of kids to interact at once (e.g., big sports activities) that can't just be arranged on the fly, at least not in many areas of the country in this day, so there has to be a structured setting for these. And at different times in her life, a kid may need different things.
(2) What I did with my kids, who were the kind to come up with their own activities, was not allow them to spend huge amounts of time in activities that I thought were more "consumptive" or addictive - e.g., television, mindless internet surfing. Truthfully, when it comes to computers I'm not sure I drew the right line; I may have been too strict (typing stories on the computer was easy for me to categorize, but what about Minecraft?). But after occasional bouts of boredom, they always came up with fun things to do. If we had lived closer to friends and could have had the same kinds of last-minute-scheduled play sessions I had as a kid, I think it would have been even better.
(3) Here's an article you may find interesting:
https://aeon.co/essays/children-today-are-suffering-a-severe-deficit-of-play
