in the Netherlands we have a better system called iDIN; it works like doing an online payment (iDeal / WERO):

* Website asks for age verification * User is redirected to their bank * Bank asks the user to log in - username/password, 2fa, bank app (whose login is behind the device's security and a secondary verification like PIN code or biometrics) * Bank tells the requester that the user is 18+, no more

This leverages a trusted party (your bank, which is subject to heavy IT security regulation and audits) and you need to show ID to open an account anyway), secrets only you know (and your kids can't easily take), phone security systems, etc. Does not require uploading ID to a 3rd party, does not require changing how IDs work, etc.

This still gives your bank a pretty good idea of what websites you are visiting though. It should not need to know this with modern cryptography.

There are people without bank account. It isn't a big part of the population (estimated to be 0.02% or about 16.000 people in Germany), but I still feel on principle this is a basal governmental function that should remain governmental and not tied to other services that can be denied to you for various reasons. This or you make having a bank account a guaranteed human right. I am fine with both.