You have to stop thinking like an engineer and start thinking like a public health official.

'Something impossible for kids to bypass' is not the goal. It's akin to evaluating a flu vaccine on the standard of zero breakthrough cases. Such a standard has no relevance on the efficacy of the vaccine.

Likewise for underage internet access. Proponents would be happily satisfied with 90% compliance. They really don't care that coverage isn't complete or circumvention is complete. Once you realize that, you can start constructing counterarguments that dismantle the claim that digital IDs would solve the problems they're supposed to.