I am speaking in particular here to Christians, believers, those maybe who grew up in organized church. I would usually say that the one truth that brings the most dramatic transformation in a person's life is the heart revelation that God is love. I still think that is true.
But then we go to a church. Then we pick up a Bible that was written in another place, another time in history, spanning thousands of years of insight, by approximately 39 different authors and in cultures very different than our own. Don't get me wrong. There is remarkable unity, progressive revelation, and clear teaching.
So how can we get this wrong: "God is love!"?