Re >> " Plenty of parents have the same debate in their own minds, or with partners and friends: Is letting kids use screens all right, and if so for how long? " As an anecdote, my mom would only allow me 15 minutes at a time of Tetris on the household GameBoy. My views on kids & screentime is pretty conservative, especially when they're younger, but my mom was down-right draconian!
It’s important to remember that todays screens aren’t the screens of yore, but quite a lot more devious. It’s fairly obvious that any negative impact of that would be larger on impressionable young minds.