It is possible to cryptographically attest to attributes like age without revealing identity.
I worked on a privacy preserving system that did this among other things. Third parties who received an attestation of some property could verify it.
To be fully private, a bit more is required. Crucially, each time an attestation is provided it is made unlinkable to previous times it may have been provided. So the third party only knows the attestation they have just received is valid, but not that it is the same unknown person they saw yesterday.
I worked on a privacy preserving system that did this among other things. Third parties who received an attestation of some property could verify it.
To be fully private, a bit more is required. Crucially, each time an attestation is provided it is made unlinkable to previous times it may have been provided. So the third party only knows the attestation they have just received is valid, but not that it is the same unknown person they saw yesterday.