You put this all down to imagination, as though that is somehow lesser that your experience of reality. How would you know which is more "real" if you haven't experienced both, and how do you know your world is the real one?
A Shamanic experience would give you a wider view of the mysteries of existence. An experience that could only be guessed at otherwise. Without it all you can do is presume to know whats going on, with it you can actually know a little more than before, just like any new experience.
I know you have trouble with your sight Susan, so this should resonate with you. Could you know, if you had been born blind and had never experienced it, what water is from a description. Would it really be adequate?