I don't see it that way at all. Nothing in the canonized text is being abandoned. Our understanding of the text, especially views based on sloppy reading and unsupported assumptions, may need to be revised. While evidence of other ancient migrations to the Americas may not fit what many LDS people assumed and taught about the text, it is not ruled out by the text. Updating our understanding in light of new evidence is not intellectually dishonest, but is the sensible way to grow with new information.
Recognizing the limited scope of the Book of Mormon and the possibility that others were in the Americas besides just those brought by Nephi is not a new, desperate tactic forced by new evidence, but a position that some careful readers of the text were advocating many decades before the DNA controvery arose. I summarize some evidence for this on my LDSFAQ page on DNA and Book of Mormon issues. Here is one excerpt to keep in mind, which is actually quoting Matthew Roper's excellent article, "Nephi's Neighbors: Book of Mormon Peoples and Pre-Columbian Populations":
Thus, the sentiments of B. H. Roberts of the First Council of the Seventy, expressed in 1909, were not entirely unfamiliar to Latter-day Saints: "It cannot possibly be in conflict with the Book of Mormon to concede that the northeastern coast of America may have been visited by Norsemen in the tenth century; or that Celtic adventurers even at an earlier date, but subsequent to the close of the Nephite period, may have found their way to America. It might even be possible that migrations came by way of the Pacific Islands to the western shores of America." He also thought it "indisputable" that there have been at least some migrations from northeast Asia to North America over the Bering Strait. [B. H. Roberts, New Witnesses for God (Salt Lake City: Deseret News Press, 1909), 2:356.] He continued, "It is possible that Phoenician vessels might have visited some parts of the extended coasts of the western world, and such events receive no mention in the Jaredite or Nephite records known to us." While the Book of Mormon text does not specifically mention such migrations, Roberts conceded that "the records now in hand, especially that of the Jaredites, are but very limited histories of these people." Transoceanic contacts may in fact have gone both ways: "It is not impossible that between the close of the Nephite period and the discovery of the western world by Columbus, American craft made their way to European shores." [Ibid., 2:357.] Thus, "even in Jaredite and Nephite times voyages could have been made from America to the shores of Europe, and yet no mention of it be made in Nephite and Jaredite records now known." [Ibid., 2:359.]Yes, others could have come to this continent besides those in Nephi's group--others from Asia, for example, and not just Asiatic Jaredites. The Book of Mormon does not require that modern Native Americans have "Jewish DNA"--if one could define what that was. Our understanding of the details of the Book of Mormon may need to be updated when we have made unwarranted assumptions. That's intellectual progress, not dishonesty.