Mobile operating systems have very great children controls. You should research the topic yourself and you will see.

I'm a parent, I have researched it, and found it not great because it still involves third parties and doesn't promote local control/anonymity without involving some external entity - i.e. Apple requires accounts, Google still gets its metrics, etc.

Unless you've got some specific better examples?

Too bad they can't prevent fully grown adults from acting like children.