Joseph teaches that there are doctrines have only become been revealed in this dispensation that were only known implicitly or not known in prior dispensations.
Section 128:18, Doctrines and Covenants, The Church of Jesus Christ of Latter-Day Saints, accessed April 5, 2022
. . . for it is necessary in the ushering in of the dispensation of the fulness of times, which dispensation is now beginning to usher in, that a whole and complete and perfect union, and welding together of dispensations, and keys, and powers, and glories should take place, and be revealed from the days of Adam even to the present time. And not only this, but those things which never have been revealed from the foundation of the world, but have been kept hid from the wise and prudent, shall be revealed unto babes and sucklings in this, the dispensation of the fulness of times.