Written in the Book of Mormon, we have a single-verse description of the devolved state of their divine connection at a point several generations past the opening of the Nephite dispensation:
"I know of no revelation save that which has been written, neither prophecy; wherefore, that which is sufficient is written." (Omni 1:11)
One could ask whether such a statement could be warranted today. In 1997, President Hinckley said:
"Let me say first that we have a great body of revelation, the vast majority of which came from the prophet Joseph Smith. We don't need much revelation." (San Francisco Chronicle, Sunday Interview)
Having been shown our day in vision by Christ, Nephi warned the modern readers of his record:
"Yea, wo be unto him that saith: We have received, and we need no more!" (2 Nephi 28:27)
Joseph Smith said:
"What constitutes the kingdom of God? Where there is a prophet, a priest, or a righteous man unto whom God gives His oracles [revelations, as in the D&C]; and where the oracles are not, there the kingdom of God is not. ... The plea of many in this day is, that we have no right to receive revelations; but if we do not get revelations, we do not have the oracles of God; and if they have not the oracles of God, they are not the people of God. But say you, What will become of the world, or the various professors of religion who do not believe in revelation and the oracles of God as continued to His Church in all ages of the world, when He has a people on earth? I tell you, in the name of Jesus Christ, they will be damned; and when you get into the eternal world, you will find it will be so, they cannot escape the damnation of hell." (Teachings of the Prophet Joseph Smith, p. 271-272)
A recent presenter at a Mormon-themed conference said:
Institutional LDS Mormonism is part of this world. Like institutions generally, there are forces at work that interfere with the practice of pure religion. Religion is only redemptive if it is pure. Therefore it is only redemptive when it can escape pollution and remain only the ideal. ...
Religion moves through two stages. In the first, God reveals Himself to man. This is called “restoration.” It restores man to communion with God as in the Garden of Eden. In the second, man attempts to worship God according to His last visit. This stage is always characterized by lack and inadequacy. This is called “apostasy.” Apostasy always follows restoration.
Abraham, Moses and Isaiah ascended the bridge into God’s presence. Through Jesus Christ, God descended the celestial bridge to live with man. Those examples all show God wants to reconnect with us. Unfortunately, the participants in a restoration leave only an echo of God’s voice unless we remain connected with God through continual restoration. Every restoration risks a lapse back into lack and apostasy.
Whether the echo is preserved through a family organization, as in ancient Israel, or through churches, as in Christianity, some organization acts as a substitute for God’s presence during apostasy. Unfortunately, organizations can only imitate God’s involvement. ...
Institutions cannot control God. (D&C 1:31; D&C 38:11-12) As faith in God is institutionalized, it becomes part of this world and necessarily influenced by cultural, social, legal and economic pressure. These forces erode faith. Religious institutions are where the ideal comes into conflict with the less-than-ideal.
Religion has always frustrated good men. Churches fail to practice the ideal. This frustration produces reformers who reject the inevitability of spiritual famine and who long for the return of a revelatory God. ...
Man is born, ages and dies. In this world entropy overtakes everything, including religion. Faith does not pause between restoration and apostasy. There is no stasis. God’s voice is heard anew when restoration is underway and the scarcity ends. But apostasy returns as the influence of this world takes over.
With time, all religious bodies confront the complex challenge of holding onto God’s word. The ever-changing present causes cracks in every church. The church will try to patch the cracks. This leads to fractures, then defections. Former believers either lose faith in the religion altogether, or faith in the church. Without God’s abundance in a restoration, pragmatic choices become policy first, then doctrine. God’s silence does not curtail men propounding doctrine, but often provokes it. (Cutting Down the Tree of Life to Build a Bridge, Denver C. Snuffer, Jr., August 1, 2014)
"Last" having meant "most recent" in Joseph Smith's day (not "final", as we assume today), the "last" dispensation of the gospel of Jesus Christ began in a much different place than modern Mormonism now occupies:
In 1832 the Lord posed this question: “For what doth it profit a man if a gift is bestowed upon him, and he receive not the gift? Behold, he rejoices not in that which is given him, neither in him who is the giver of the gift.” (D&C 88:33) From the moment Joseph Smith died those who believed he was a prophet began to lose memory of what God revealed through him. The pace of forgetting has accelerated.
The obligation to respect Joseph’s revelations is clear from the Lord’s instruction, “no one shall be appointed to receive commandments and revelations in this church excepting my servant Joseph Smith, Jun., for he receiveth them even as Moses.”2 (D&C 28:2) When Joseph was slain the church wanted a replacement. When no one with his gifts was available, an imitation served.
On August 8, 1844 the quorum of the twelve were voted to lead. By December 1847 Brigham Young no longer wanted to share power with eleven others. Against Wilford Woodruff’s recommendation and the active opposition of John Taylor and Parley Pratt, Young successfully won a vote at Winter Quarters making him the second president of the church.3 From Young until David O. McKay in the 1950’s, when the word-title “the Prophet” was used it still meant only Joseph Smith. But rhetoric matters, and the word-title began to be used to first secure acquiescence, then to compel compliance by LDS Church leaders.
The church’s presidents' claim that they too could communicate “commandments and revelations… even as Moses” began the process of accelerating our forgetfulness4 of Joseph’s words. He became less important as successors claimed equality. Who cannot see the logic in preferring a “living” prophet to a deceased one? Ignoring Joseph means forgetting. By forgetting we have refused the gift God offered. Our first obligation now is to remember. Until we remember what was given before, there is no reason for God to give more. (Preserving the Restoration, Denver C. Snuffer, Jr., Introduction)
1 Teachings, revelations, and epistles to the Church from Joseph Smith, as well as, the epistle to the church from Hyrum Smith after he was appointed prophet to the church by the Lord and elected president by the church are not included in modern LDS scriptures, and thus are not included here. (In fact, Hyrum is not considered to have ever been prophet or president to the church.) The inclusions of Joseph's additional teachings and epistles could certainly be justified due to the Lord's direction in D&C 21:5, which commandment from God concerning Joseph is unique in all LDS scripture. Thus sermons delivered by Joseph and partially recorded, as in Teachings of the Prophet Joseph Smith or The Words of Joseph Smith, would otherwise be included. Additionally, D&C 7 is shown as a translation, since it was claimed by Joseph to have been a translation from an ancient parchment, written and hidden up by John the Revelator. (see the Book of Commandments, Chapter 6) And D&C 136, though sometimes thought or believed to have been a revelation, was clearly only a committee-authored, Brigham Young-approved epistle to the saints.
2 The revelation allows for the possibility for someone else to be later appointed “in his stead.” (D&C 28:7) It would be through Joseph, however, the power was given “to appoint another in his stead.” (D&C 43:4) That appointment came in January 1841 when Hyrum Smith was appointed. (D&C 124:91-96) Hyrum, however, was slain moments before Joseph, and therefore no one else has been appointed to amend, supplement, disregard, alter or reject commandments and revelations given through Joseph Smith.
3 Technically he was the third, but no one counts Hyrum Smith despite his actual appointment and service.
4 Forgetting includes re-interpreting the language by divorcing it from context, supplying new meaning not originally intended, and improperly using Joseph to vindicate later improper innovations.