We wish that Moroni had been allowed to record this vision in greater detail. But as king Mosiah knew great things which were too sacred to be revealed until after Christ's First Coming, Moroni knew great things which were too sacred to be publicly revealed until after Christ's Second Coming. Yet someday, as promised, the things revealed to the brother of Jared will be revealed to us if we follow the counsel of Ether 4.
Bruce R. McConkie
"Even the true saints-the believing disciples, those who have accepted the gospel and received the gift of the Holy Ghost-are not prepared to receive all things. We have the fulness of the everlasting gospel, meaning we have every truth, power priesthood, and key needed to enable us to gain the fulness of salvation in our Father's kingdom. But we do not have, and are not yet prepared to receive, the fulness of gospel truth.
"This is perfectly illustrated by the fact that we do not have the sealed portion of the Book of Mormon. That treasure-house of Holy Writ contains an account of the creation of the world, of the dealings of God with men in all ages of the Second Coming of the Son of Man, and of the millennial era when the earth shall rest and Zion prosper to the full-all of which we are not prepared to receive. The doctrines revealed to the brother of Jared, and which are recorded in the sealed portion of the Book of Mormon, were had among the Jaredites; they were known to the Nephites during their Golden Era; certainly they were known and taught in Enoch's Zion; but when the Lehite people 'dwindled in unbelief,' Moroni was commanded to 'hide them up.'" (Mortal Messiah, Book 2, p. 237)