There are a couple references to the Gospel in the scriptures I think are worth a lot of thought.
These are the phrases:
"The lesser portion of the Word" (Alma 12:10)
"The greater portion of the Word" (Alma 12:10. 3 Nephi 26:9)
"Preparatory Gospel" (D&C 84:26)
"Much of my Gospel" (1 Nephi 13:34)
"Fulness of the Gospel" (3 Nephi 16:10, 3 Nephi 20:30, 1 Nephi 15:13..there are many)
"Preparatory", "Much", "Fullness" These are interesting words that suggest the Gospel has levels. Sometimes the meaning of these words can degenerate over time, especially if they are not taught or are not present in the publications or manuals we study.
It says in the introduction of the Book of Mormon that that the fullness of the everlasting gospel is contained inside it. So does that mean we, as a church, have the fullness? I hear frequently at church that "we have the fullness". I wonder if it would be more correct to say that we have the fullness available to us. Bit of a difference. One suggests we need to take action, the other suggests we don't really need to do anything as we've already obtained everything God offers and it will be handed to us on a platter at some future time due to how special we are. The fullness existing in a book you believe in, or Book the religious organization publishes is not really the same as "receiving a fullness". Huge difference.
To know the fullness is in the Book of Mormon can be a great thing. But that knowledge may also lead to the members having a nice quantity of misleading assurance.
Isn't it comforting to have that assurance that we have the fullness? That makes one feel wonderful, special, chosen, and..... complacent. Why reach for a fulness which you already have?
The thinking also sometimes goes that if we have it (the fullness), that means no one else out there has it. This may all lead to mistakenly assuming we are uniquely superior, and can sit back, relax, chant that "all is well" and smugly think we can coast along and just do what we're told. And if it so be we missed some stuff or were wrong on things, at the last day God may beat us with a few stripes, but in the end we'll still be saved in the Kingdom of our choice. Because after all, we had the fullness. As if having a recipe for bread was the same thing as being filled by the bread you chose to prepare cook up, and partake of.