I went to a Steiner school for kindergarden and the focus is completely on play and hands on outdoor activities. I have fond memories of messing around with hand drills in the playground!
Adults who can perform knowledge work and have sufficient impulse control.
I believe that sitting children down for a couple of years, compulsory, is a strong factor in what we call civilization and the overall decrease in violence. You can think of it a bit like Zen's "just sitting" meditation practice, if you want.
My kids' daycare has adopted it. It seems perfect for my daughter who seems self-driven, but maybe too open-ended for my son (who we pushed ahead..so far - mid-november bday with 10/31 cutoff).
I can't say that nobody gets some benefit from the drugs, but having grown up with some friends on them in elementary/middle school I can safely say it's a serious thing to be on, and it's not to be taken lightly.
Humans are just highly intelligent animals. Kids acting like animals when they are 5 years old is not unnatural.
[1] https://www.houstonchronicle.com/local/gray-matters/article/...
[2] https://www.scholastic.com/teachers/articles/teaching-conten...