No offense but if you're proposing a solution that involves whitelists... that solution has already failed.

The web is too big and changes too much and that's before we get to the issue of applying laws to a whitelist based on different juristictions worldwide.

And I have to question, who would administer it? The parents? They won't. Google or Apple? Why do they want to deal with irate parents or culture wars around what is or is not on the list?

There is obvious increasing demand for this from parents, politicians are going to act on it, I think a "this is a child" header is the only one that actually really works. It works for the parents because it's easy to setup. It works for websites because they can cleanly identify a child and filter content if appropriate.

It seems to me that every other solution than a "this is a child" header is either impractical or way worse.