This is a doctrine that we are too prone to shy away from, to hide from, to shun. But it is true. It is vital. It is central to the gospel of Jesus Christ. Indeed, if we do not believe in and accept and teach properly the doctrine of the Fall, we cannot, worlds without end, teach properly the doctrine of atonement.
To teach atonement without teaching fall is to relegate Jesus to no more than a guide, a great teacher, a coach, or an inspiring cheerleader. Jesus Christ is the Redeemer, the Savior, the advocate between a fallen and unholy people and a Holy Man, even the exalted Man of Holiness.
He came not just to teach or to encourage. He came on a search-and-rescue mission. Truly, because of the Fall our natures have become evil continually, and those natures (not merely our behavior) must be changed and renewed; we must be brought back from death, spiritual death, through the mercy and grace of one who has power over death. We must be reborn. It is noteworthy that these words were not spoken by Laman or Lemuel or one of the score of apostates or inactives in the Book of Mormon.
They were spoken by the brother of Jared, a righteous man, but one who knew well his weakness, one who knew clearly his limitations, and, most important, one who knew the source of his strength. (For a detailed treatment of the Fall and its consequences for man, see Robert L. Millet, Life in Christ, chapters 3-4.)