I don't agree. What's the next step? Will they ban me? Is it my responsibility to reach out to them and tell them I disagree? Or am I just expected to never go to Medium again?
To be GDPR compliant, everything needs to be opt-in (except for the stuff that is critical to functionality). If you refuse to answer their questions, they need to assume that means "no". From this you can see that it's not your responsibility to tell them anything and you can still use their website just fine.