I don't want "papers please" to be normalized. If the smart ID can do anonymous attestation of age then it can presumably also share various details with a requesting party. Next thing you know Facespace 365 is requiring you to provide your (attested) full legal name in order to register an account. I find that to be a highly objectionable outcome.
If things escalated beyond basic age checks that also adds hardware requirements. Would I find myself needing a smartcard reader to do anything online? The friction of needing to visit a bank in person seems like a feature to me.
What doesn't bother me is age restricted content guarded by a low fence. The bare minimum required to blunt the impact of something that appears to be analogous to an epidemic.
However, we're not going to get that because politicians would just say it is open to abuse. Anyone can go to a liquor store and supply alcohol to minors. The same would apply to anonymous age tokens. I don't know if it would be a big issue in practice, but it will in the minds of politicians.