The Internet should be Unrated and thus Adults Only by default. Just like public spaces. (Would you allow an 8 year old to wander New York City unattended? Arguments can be made for more controlled spaces but...) Have a website and want the chance for kids to see it? Advertise in the headers that it's moderated and intended to be a given rating. Various indexers can pick that up. Complaints can be forward to relevant…
Many people do, in fact, do this:
https://reason.com/2021/06/11/free-range-kids-second-edition...