I've never heard of a single student of the Bible becoming a Bible scholar and then subsequently "realizing" that Mormonism has the actual Gospel spoken of therein.
Neither did apostate Christianity produce the LDS Church yet the doctrines are there plainly in the Bible. It obviously takes a level of spirituality and/or revelation to see them.
What knowledge is it exactly that Mormonism posseses that mainstream Christianity doesn't? I can understand the argument of authority and right to perform necessary ordinances, but new information? I don't see much.
Authority ought to be enough. But it is certainly evident that without authority, truths are lost because there is no revelation or spiritual understanding necessary to see what is plain before one in the scriptures. Examples besides authority would be:
Nature of God (Anthropomorphism, Subordinationism, plurality of, etc.)
Requirements for salvation (Water baptism, works, etc.)
Salvation (Degrees of, preaching of the gospel to the dead, LDS-style Theosis etc.)
Extra Biblical scripture
etc.
There are very significant differences between us and other Christian churches and all are found in the Bible and all seem to have once been extant in early Christianity but no longer.