The Bible is the "mouthpiece of God" and the ability to hear and understand that "mouthpiece" is given by God alone through the work of the Holy Spirit.
You invest the title of "mouthpiece of God" in fallible men when God tells us His "every word is pure" and leads to a correct understanding of His will and our lives within that will.
It's just not that difficult, but men enjoy making it seem difficult. Probably because for some of them, it is difficult and very near impossible to understand.
As God wills.
And what is the source of this "pure" word of God? The Bible? The same bible that exists in thousands (literally) of versions, in different text-types, of different length of chapters, with all the omissions or deletions or additions or errors? Why, next thing you will tell me will be that God drop-shipped KJV to Luther, Calvin and Zwigli with instrustions how to interpret it. LOL! Talk about dark ages! Get real.
Also, the more complicated it becomes the less inclined people are to try and understand. Then individuals are more willing to just trust whatever those in "authority" tell them.