Symbolism: Understanding this verse depends on understanding the vineyard’s “loftiness.” While “loftiness” is a frequent synonym for pride, which certainly plays a major role in the Book of Mormon, that meaning does not fit well with the image in this verse. Rather, “loftiness” occurred “because the branches have overcome the roots thereof… [and] grew faster than the strength of the roots, taking strength unto themselves.”
The servant agrees that the master’s efforts have been sufficient. The fault lies in the overgrowth of the grafted branches. Ironically, the master’s efforts over-succeeded, for the grafted branches grew faster than the strength of the root allows. The fault lies not in the Lord, but in the branches.
The allegory therefore squarely places upon humankind the responsibility for the gospel’s failure (up to this point). Theologically, this message is significant. The temporary failures of the covenant’s full efficacy are never due to the Lord’s actions but always to our own.
Reference: Andrew C. Skinner, professor of ancient scripture at Brigham Young University, notes a similarity between the top-heavy branches overcoming the root and a later saying current during Jesus’s time:
“He [Rabbi Eliezer ben Azarya] used to say: One whose wisdom exceeds his deeds, to what is he like? To a tree that has many branches and few roots, so that when the wind comes, it plucks it up and turns it over.” This saying also reminds us of a similar concept expressed much earlier by the ancient prophet Jacob [sic, the prophecy of Zenos as recorded in Jacob] and seems to corroborate the authenticity and antiquity of such images in the prophetic teaching of the Book of Mormon.