Abstractly perhaps, but I'm not aware of any practical enforcement mechanism I'd classify as "good".

If the operators are liable, they will find a way, it's easy for the operators to infer a users age based on usage patterns. They must be required to close these accounts.

It doesn't need to be perfect, but in spite of that perfect is possible if people ask for it. Don't tempt them. Look at what happened in Spain with Cloudflare.