The fact that Joseph Smith Jr., questionable as he may have been in his ethical choices, built a religion on 1) a continuing prophetic line of succession and 2) an open scriptural canon shows Mormonism and the LDS movement to be the most “honest” Abrahamic sect.
Every other Abrahamic sect, save for the Bahai, has operated on the claim of preaching the final and closed testament of a deity and its works on Earth, as well as an extinct line of prophetic contributors to scripture. The LDS movement, on the other hand, challenged this notion in such a flagrant way that they were chased out by Christians of the then-current states of the Union in the 19th century.
This also benefitted strongly from improvements in publishing technology in the 19th century, which allowed more mass publication of printed books and a reduction of cost. If most Abrahamic religions originated from the times when books were still hand-copied by scribes, would it really make sense to rely on such a scarcity-driven paradigm of “revelation” when books and printers were more plentiful?
The LDS refused to comply with this deliberate conceit of a “sealed revelation”, or of over-reliance upon interpretation of scriptural literature, and inaugurated a continuing expansion of scriptural literature. The implied “scarcity” of revelation was rendered moot, and the LDS movement made their “Doctrine & Covenants” more of a “Living Word” than Christians consider their Bible or Muslims consider their Qur’an.
I say all this as an atheist.