the results are indeed relative. the smarter one gets the same thing still applies. it's a theory not to point at others and say 'he's on mount stupid'.. but rather one to be wary of yourself being on this curve, which in some sense or aspect one always is, as one is never a master of everything in their lives. it's a theory about evaluation of self only applicable in that domain.
This is a really bad summary of the original D/K paper, both misleading and incorrect. Maybe this illustrates nicely why the article was needed. They didn't knowingly test any dumb people; it wasn't a random population sample, it was all Cornell undergrads volunteering for extra credit. The results are relative, not absolute, they were being asked to rate themselves against the population (their classmates), not actually rate their ability. That involves guessing how good others are. We don't know how good they all were in absolute terms, only their relative scores. The results did not conclude anything close to "always", it only showed an average bias. The results show that, on the tasks they tested, the people with the best skills under-estimated their scores relative to their peers.