Idea is great, motivation is great, but as usual:

It’s the net. You simply can’t enforce that. Technically. It might help a literal handful of totally technically challenged kids to not gain access. Unless they have friends who’d show them how.

And even IF it could magically work, big tech could simply ignore that. See e.g. steam, who, instead of enforcing age-verification for Germany, they just totally banned access for Germans to relevant titles. “Not worth the hassles”.