Armand L. Mauss maintains that the endowment developed out of a Masonic cultural context, concludes it is not a "big issue."
Armand L. Mauss, "Culture, Charisma and Change: Reflections on Mormon Temple Worship," Dialogue: A Journal of Mormon Thought 20 (Winter 1987): 80
Frankly, I have some difficulty understanding why this should be such a big issue, except to those with a fairly limited understanding of how a prophet gets ideas. Since prophets and religions always arise and are nurtured within a given cultural context, itself evolving, it should not be difficult to understand why even the most original revelations have to be expressed in the idioms of the culture and biography of the revelator.