I'm mostly with you. In fact I've often wished that browsers did more things like that, for example cookie warnings. The cookie warning thing is a ridiculous misunderstanding of how things should work. The server doesn't store things on your PC, it just offers them to your browser, it's up to the browser to return them or not, it doesn't even require new protocols.

But of course kids are resourceful and will find a way of accessing content they want to access, for example maybe using a games console or something a parent might not immediately think of as having a browser.

Whether it actually makes sense to protect kids from themselves to that extent I think is a valid question which I'm not sure I have the answer. I know passing around CDs full of such content was common when I was young (in the early days of the internet).