Seems simple until you try to figure out what's allowed for what age, which surely will differ by country at a minimum.
(if there are further restrictions then it gets messy, but I feel like that's the current state of things anyways? at least for online services which I'm mostly speaking about here.)
Mostly my point is I don't think attestation is required. I think that responsibility should fall upon parents, and I don't want to have to give my ID to any online sites, because I don't remotely trust them to keep that safe. I'm less worried about them storing a number I send them about how old I am.
And 50 US states.
Having no restrictions would be great, but since a bunch of countries are passing these laws I'd appreciate having a minimally invasive version instead.