The center of existence is not humanity. It's God. :) Humanity is simply an expression of God, made with the most splendor & beauty of all creation. But we aren't God, and we simply can't handle knowing good and evil, as God can. Our limitation as human beings is that we aren't made to be totally self-sufficient. We aren't made to be completely all-knowing. We aren't even made to be perfect, in the popular sense of the word. We just can't handle it, and such a design was never God's intention. We aren't made to erect dense moral systems or follow long-winded ethical codes, to create exhausting ways to restrain our behavior and force those on other people to keep them "accountable." Most of these methods—even the over-spiritualized "Christian" versions—don't even work, or rely on guilt, fear and shame to do so. Our fallen world operates this way today, as well as many churches and Christians, but this is not the way God created us to exist.
We are made to be loved and fulfilled by God, through everlasting fellowship with Him. Only when that happens will humanity's full potential be realized, because we'll finally be at peace within ourselves. And from such peace we will live, along with the joy and the love and the fulfillment and the hope and the righteousness that come along with it. And then, we can lavishly share these beautiful things with all those who'll take a moment to stop and listen. They'll hear, maybe for the first time, of a God who not only saves and restores, but is a river of living water; a deep well that, once you drink from it's waters, will fulfill every need, and never leave you thirsty again.
How about that for purpose. :)