Sure: if we believe that having a giant third-party in the sky that does verification of users itself a giant privacy violation that the web currently doesn't require us to subject ourselves to--and if we also believe that the information they collect won't be invasive, particularly when dealing with an international context--I absolutely agree that we can then use various cryptographic schemes to protect our information from the provider.

However, I certainly don't believe that: I believe that having a giant centralized verification service is inherently dangerous in a world where we are apparently reliant on inanity like CrowdStrike to feel a sense of security; and, in fact, there was even just recently a big hack of an identity provider company.

https://www.eff.org/deeplinks/2024/06/hack-age-verification-...

You don't need a centralized service. In the US, individual states are adopting[0] the ISO 18013-5 mDL standard, for example, which allows each state to be authoritative on identity information for its residents (or, if I understand it correctly, something like "isOver18" signed attributes).

[0] https://www.mdlconnection.com/implementation-tracker-map/

The "giant centralized verification service" can be some entity that already has your information such as your government.