If the governments would get their shit together, we could have something like age assertion with the eid chips in our IDs. Imagine that. The important thing is that website.com just asks the government "is this user an adult?" And the government replies "yes". No information besides the relevant one is provided, and it's through a trusted authority.
Yeah, not gonna happen, just like using the keys in my Personalausweis to send encrypted mail.
Just because everyone is ill, doesn't mean it's not an illness. Argumentum ad populum