For example, Apple and Google should provide tools for the parents to set up a device appropriately for a child, much like the shop should not sell alcohol to underage customers. Similarly, content producers should specifically need to label content targeted for children or specially 18+, like the producer of alcohol must warn customers on the label and inform the retailers.
Parents and caretakers need information to make an informed decisions before being able to consume the media themselves. They also need some granular tools on the device to avoid banning them entirely. The burden is shared between creator, distributor and consumer.
We already had laws for this and it makes sense for some type of access control to the open internet. The shocking part is the requirement for everyone to verify ID to multiple public and private institutions, more than once per.
An analogy for the UK now would be needing ID to enter the supermarket (access the internet), ID to look at anything aimed at adults and potentially harmful such as alcohol, chemicals, sugary food, medicine etc. (know "potentially harmful" subjects exist), ID to look at anything lawfully 18+ such as alcohol and cigarettes (view the content), then ID again to make the 18+ purchase from an account needing ID to open.