I guess I really didn't make myself clear. I'm not saying that Ichigo is retarded or anything, far from it. Ichigo is very smart, a lot smarter than the average person. But he has a different kind of intellect. His smarts are more instinctual like battle instincts, and the ability to deduce, and perceive others feelings, and true intentions. He has acute emotional awareness, and his perception during battle is the best there is. That in itself is a form of intelligence.
But on the opposite analytic side, Ichigo is lacking. Coincidentally, this seems to me the kind thinking one would need to be a powerful Quincy. And again, as smart as Ichigo truly is, I don't see how anyone could believe that he is comparable to Ishida, Urahara, Kurotsuchi, or even Aizen. There is too great of a gap between them in terms of raw intellect.