"For my soul delighteth in plainness; for after this manner doth the Lord God work among the children of men. For the Lord God giveth light unto the understanding; for he speaketh unto men according to their language, unto their understanding. 2 Nephi 31:3
I like hearing this, a prophet of God glories and delights in plainness. That's encouraging to me. He says after the manner of plainness doth the Lord God work among the children of men. This is not the incomprehensible, unknowable God of some Historic Christian creeds. Nephi is talking about a God who speaks according to my language and my understanding. How refreshing, for once I don't need another college degree.
The opposite of plain is fancy, ornate, or complicated. Sometimes things that have little merit of it's own need those things to compensate. It needs slick marketing, and all sorts of bells and man made light in order to appear to have value. Fancy and new ornate things will often catch the mind and are often used intentionally because marketers also know about to catch our attention. But the truth doesn't need that stuff. The truth reaches my heart all the time without it. I find that also to be refreshing.
I like what Nephi says: The truth is plain. It's how the Lord works. This isn't to say some issues are not complicated, because they are. But I've noticed even things I thought were complicated, can, with light, become plain, and understandable. It spoils you in a way, and thereafter all the worldly marketing gloss, and pretty advertising paint are much less alluring.
When the scriptures say our minds are darkened, and blind, this gives me pause. For the Jews, Jacob tells us their blindness of mind came from "looking beyond the mark" Jacob 4:14. Sometimes it's easy to look past the plainness of the "Word of God". "The Word of God" is Christ (John 1:1). He is what we should look to, otherwise as vs 14 says, they/we will stumble and fall. The members of the Church are the ones who claim to have a testimony of the Book of Mormon, so we should read such words as if speaking directly to us. Otherwise we are blind to the plain and simple words written.
I have a testimony of the plain and simple nature of the truth. It gives light to my understanding, it engages my mind in a way that is enjoyable. Often it's counter-intuitive and requires me to change. So it's not always easy, but it's plain, and according to "my language" as Nephi says. It's as if God wants us to have confidence we can understand His words. I think he does.