Well, in Lucas' defense, a common misconception regarding midichlorians is that they are the Force. A lot of people seem to think this, and its not really true. I didn't mind the midichlorians in TPM because it never really took the mystery out of what the Force is, it just explained how it can physically link to the material body of the person using. Midichlorians are conductors of the Force--the more midichlorians you have, the greater you conduction of the Force will be. The end result of course is: amount of midichlorians=amount of Force power, so it almost is like the midichlorians are the Force itself, because they might as well be.