The following passages clearly indicate that Joseph’s seed (white race) would be destroyed and that only the red/dark (Native-American) race would survive. This includes all of Joseph’s descendants.
A God who would make promises and then break them is certainly not immutable or unchangeable (as mentioned by Bruce R. McConkie in Mormon Doctrine, page 318).
What sort of deity has foreknowledge or omniscience when he entrusts the fullness of the gospel to people who were ultimately annihilated? Some LDS writers have tried to explain this contradiction by claiming that destroyed does not mean annihilated.
Moroni stated that he alone was left of all the Nephites, and that there were none left but Lamanites. If the Nephites were not annihilated, then the Book of Mormon does not demonstrate the clarity Mormons espouse.
Furthermore, if any Nephites survived, where are they? (Perhaps the nebulous doctrine of the Three Nephites?)…
“And now it came to pass that after the great and tremendous battle at Cumorah, behold, the Nephites who had escaped into the country southward were hunted by the Lamanites, until they were all destroyed. And my father also was killed by them, and I even remain alone to write the sad tale of the destruction of my people. But behold, they are gone, and I fulfil the commandment of my father. And whether they will slay me, I know not. Therefore I will write and hide up the records in the earth; and whither I go it mattereth not. Behold, my father hath made this record, and he hath written the intent thereof. And behold, I would write it also if I had room upon the plates, but I have not; and ore I have none, for I am alone. My father hath been slain in battle, and all my kinsfolk, and I have not friends nor whither to go; and how long the Lord will suffer that I may live I know not.”
Joseph Smith, Jr., Book of Mormon – Mormon 8 (Salt Lake City, UT: The Church of Jesus Christ of Latter-day Saints, 2022/online edition), 2-5.
“And now, after that, they have all dwindled in unbelief; and there is none save it be the Lamanites, and they have rejected the gospel of Christ; therefore I am commanded that I should hide them up again in the earth.”
Joseph Smith, Jr., Book of Mormon – Ether 4 (Salt Lake City, UT: The Church of Jesus Christ of Latter-day Saints, 2022/online edition), 3.