> I'm wondering if this would be a reasonable solution to preventing the exploitation of minors on the internet

The bulk of exploitation comes from

1. Big tech. I imagine that 90% of "internet for kids" would be Cocomelon AI-generated slop

2. Other kids bullying each other

Not to mention the simple fact that if you shelter kids from any adult content then they'll turn 18 while still having child-like mindset, which means that "exploitation of kids" will turn into "explanation of young adults".