The issue is how it will be enacted. It will invariably require transmitting personally identifying information across a network and for it to be stored somewhere for processing. Even if this is done as safely as possible with government systems, there is always the risk of data theft and exposure as well as excluding people that don't trust the government at all, like pretty much every Indigenous person I've ever met.

It as well provides the government with a system and store of information that could be used as tool of oppression.

Australian/Canadian here.

I can assure you that kids in Australia are just using VPNs. You need global type of ID system to get around VPNs from a specific place. That didn't turn out well for Discord when they tried to implement global ID.

My solution is government signed Zero Knowledge Proofs for age. Be weary of anyone who says we need to take away your freedoms to protect the children, when there's easy ways of doing it without taking your freedoms.