This is what I think. I saw someone else on HN suggested provide an `X-User-Age` header to these sites, and provide parents with a password protected page to set that in the browser/OS.

Responsibility should be on the website to not provide the content if the header is sent with an inappropriate age, and for the parent to set it up on the device, or to not provide a child a device without child-safe restrictions.

It seems very obviously simple to me, and I don't see why any of these other systems have gained steam everywhere all of a sudden (apart from a desire to enhance tracking).