There's a fairly non-invasive way to do age verification: ID cards that connect to a smartphone app that only provide a boolean age verification to the requesting service. Requesting service can be anonymous to the ID app and the requesting service can only receive a bool.
That most implementation will try to collect far more data is the real concern.
There's an even easier one: When you buy a phone, the salesman checks your ID and sets the phone to child lock mode or unlocked mode.
The goal isn't child protection but surveillance and profits for kyc companies.