I don't believe the universe is relative, however I believe consciousness creates the illusion of relativity. IOW, our experience of the universe is a relative one even though the universe itself is not. Subjectivity is a mirage IMO, which I suspect will become less mysterious as we learn more about the mechanics of the brain.
My source of knowledge is success. What continues to works is knowledge that it continues to work. What has been shown to not work is knowledge of what doesn't. Knowledge is good only for as long as we can successfully use it.
Subjectivity is not particularly useful beyond the individual experience, firstly as a said, I see it as a mirage, secondly, while I can have knowledge of my own subjective experience, I can't have knowledge of yours.