Again, I don’t know. Self esteem is part of the answer, but the other part of the answer is a better understanding of ourselves. We don’t need to be interested in everything, but we should have an idea of what we’re interested in — or, in the least, an understanding of how to identify the feeling of “interest.” That, and then an honest understanding of our own values, and what actually matters to each of us as individual human beings in a vacuum.
…en you don’t care — and you don’t care that you don’t care? Sometimes professional therapy is best. But short of that: find at least one (healthy) thing you do care about, dump energy into it, and build from there. The rest, for most of us, will work itself out..