I think the obvious solution to this is to require websites not ask the visitors age or name. Like, that stuff is private info, and they don't need it to provide whatever service they're providing.
As for categorizing content in general, I think it's pretty safe to look at Facebook and Twitter for examples of content moderation failing in spectacular ways, just as it is by all of the horror stories of Google accounts being automatically locked for utterly unclear reasons because some automated system picked up some cue and erroneously banned the account.
Maybe some other platform does this right, but I'm skeptic. I've watched some TikTok with my niece and some things were way over her age.
Maybe I'm getting old, but at least on TV there was a timeslot marked as suitable for all audiences, enforced by some agency in each country.