If you don't want your kid using the internet then don't let them. No need to throw the whole society under the bus.
I don't agree with the approach from the Australian government and I don't see that at being effective but regulating shady companies using deceptive techniques to maximise their profit is a necessary thing.
Personally I think differentiating impact on kids/teens and adult is a mistake and the approach should be around really strict control on data collection as well as strict control on the use/abuse of manipulative techniques to create addictions.
Australia tends to be more willing to make collectivist decisions like this, unlike America which places immense value on individual choice.