Instead of arguing on the bad this brings, we should push our authorities to enforce mechanism that still respect the anonymity of a person.
France's "France Identité" started to implement an approach that respect anonymity by using what they call a "double anonymity: a principle that ensures that neither the adult site nor the age-appropriate provider can know who is accessing what. Using advanced cryptographic technologies—digital signatures and zero-knowledge proofs—the system generates proof of age without revealing identity or browsing history." (source: https://entrevue.fr/en/police-justice/verification-dage-sur-...)
French's state should already have these informations from us (as a French citizen) so asking them to provide a certificate that guarantee my age seems like an obvious choice, and giving that digital certificate to any site without having to tell the issuer where I'm going is, I think, the best solution for the worst project.
(There a lot of news about this, but mostly in French. If you are curious:
- https://www.franceinfo.fr/societe/pornographie/l-arcom-impos...
- https://www.frandroid.com/culture-tech/web/2962099_france-id... )