How about phones and computers themselves can be configured as belonging to children, and services/platforms being required to respect rules when a device tells them a child is accessing their services?

In terms of YouTube all I want as a parent is (a) to ban Shorts from my kids accounts (b) be able to see a list of what they're watching. I want this respected on the app and website.

Good platforms have decent parental controls. Bad platforms don't. YouTube is just awful in that regard. Which is a shame, because there's a tone of good stuff to watch on YouTube. But it's on them to fix their platform.