A lot of the criticism is based on the concept that it won't be technically watertight. But the key is that it doesn't have to be watertight to work. Social media is all about network effects. Once most kids are on there, everyone has to be on there. If you knock the percentage down far enough, you break the network effect to the point where those who don't want to don't feel pressured to. If that is all it does, it'…
In the EU you don’t need to upload your ID anywhere, the service can use the government’s portal for ID verification. In the case of age verification they can get a yes/no response if the age is above some threshold. This is opaque to the service so they wouldn’t get any additional ID details.
And that's assuming the technical solution is deployed everywhere. I'm in the EU with one of those IDs, and I still had to upload photos of my passport and scan my face to open a bank account. The identification process even had its own app that I had to install.