Although it is an old thread I came across it by a google search since I have the very same problem. I have no problem with my vision nor the coverage of my camera. Yet I noticed that no matter how hard I try, my images often come out horizontally / vertically incorrectly aligned, and with a meaningless composition. I have to crop and angle almost all my images in post. I have been shooting for many years and so far I haven't used the LCD at all because I didn't even think about using it for shooting. Recently I had to try it out and I was surprised how I immediately noticed those things that I can't see through the viewfinder. Your explanation about how the brain works sounds convincing to me, and I will try to use the techniques that you mentioned.
