Exactly! We already have content tags on TV/Movies, just extend it to the web and make mandatory.

I imagine it could be not trivial to enforce (esp. for offshore web) - but definitely easier than enforcing the same sites to implement much more complicated identity verification (while preferably also not leaking this data).

But that might not even be necessary. A small on-device AI can probably do a decent job classifying pretty much everything we don't want children to see - with and option for parents to override it when needed.