Think of the images from the world over of indigenous women going about their days largely with their young children strapped to them.
Until they can walk at which point they are increasingly gone to do the vital growing that happens away from adults.
And by the time they are 5 they play alone unsupervised. Which was even the same in villages in Europe even after WWII. My grandma was herding goats with pack of kids at 5 and remember it as normal. School started at 6.
Note how the extent you went is imagery rather than hard numbers, you don't have a leg to stand on.
This is literally based on a comparison with hunger-gatherer societies.
To the extent that there is any accuracy to your "compared to historical standards", its probably based on a low point reached (in the "developed" world) somewhere between the first industrial revolution and mid-20th century,
We, the supreme civilisation, at the summit of evolution, are locked in in individual cages, disconnected from each other, so we can spend more quality time attached to our screens.
We are “civilised to death”
This seems to assume that ~all attention is positive and that attention is still beneficial after the Xth hour. After a time the adult role becomes less parent and more like prison guard duty.
It also seems to assume adult-time is enough for kids and that peer-only time isn't an irreplaceable environment for kids to develop their core social skills.