This doesn't work because you can't prove the origin of a single bit of data without the associated identity and the origin of the data can only be verified by matching the biometric image on the ID against your real face with a camera.

Otherwise a single person could donate their ID card and let everyone else authenticate with it.

Now you might counter and say it would be enough to give each card a sequential number independent of the person's identity, but then you run into another problem. Each service might accept each card only once, but there are many services out there, so having a few thousand donations could be enough to cover exactly the niche sites that you don't want kids to see.

There is no way to implement this without a complete authoritarian lockdown of everything. There will always be people slipping past the cracks. This means all this will ever amount to is harm reduction, but nobody is selling it on that platform. Nobody is saying that they are okay with imperfect compromises.

Ah, so your phone is the trust point. That's better than it could have been, but it still leaves other issues, like sites with multiple domains or data brokers cross-identifying you based on phone and user information, e.g. 'this phone verified someone on porn site A. This same phone over on social media site B also verified, and on the social media site they have all their real-world info, so now we know their interests', etc.

And before anyone asserts that the phone can be anonymous, that doesn't work, otherwise you can just have an app that claims to have a verified ID attached.