> Especially when the law says it's illegal to deny service based on their cookie preference, but some services are literally impossible to provide without a cookie of some form.

To clarify what others are saying here - it is illegal under GDPR to deny service based on people opting out of providing PII in the cases where that PII is not needed for providing the service, not for refusing to accept cookies (although, sure, there can be some relation between these things).

If for example you were providing a service where you sent someone emails on their birthday with autogenerated Love from your AI Momma messages it would not be illegal for you to refuse to provide them access to your service if they opted out of you storing their email and birthday, because those two pieces of PII are needed for the service to work.

That said, most services do not need to store any PII for any length of time to work. Thus if a service says you can't read our medical advice column unless you allow us to store all this stuff we just hoovered up from your browser forever, that would be illegal. Because they don't need any of that stuff to show you the article they already have written and ready to go.