Well yeah, thats a problem with debates, if people are using different definitions then you end up talking around each other. I don't think the definition I use is unreasonable though. Slavery is fundamentally a matter of self-ownership, and taxation robs you of such self-ownership. Requiring resources to survive doesn't rob one of their own self ownership. Neither does working for a salary, although "wage slave" gets thrown around without much opposition to the term...

Anyways, rights exist a priori, regardless of the capacity for any power to enforce said rights. Negative rights don't actually require enforcement because they aren't coercive. Implying rights don't exist because people violate them doesn't make sense, it's irrelevant.

Think through your example about the doctor. If you (a doctor) and I are stranded on an island and I break my leg, the "right to healthcare" would imply that you are obligated to help me, and I have the moral right to coerce you (violently if required) to help me. Would you agree to this proposition?

Now of course most people who hold these beliefs haven't given it any thought beyond "I want people to be safe happy and healthy". But those who have, realise coercive violence is a base requirement and are fine with it, but obviously won't frame their beliefs in that way.