This is lovely. I know you're discussing canonical characterization, but when you said this:

But with writers, there's a new element -- they are the ones in control of their object of affection. Because of this, there's no reason for the writers to move beyond the state of infatuation. There's no reason to change their beloved out of the mold that they adore them in.

I finally realized why I've been having so many problems with certain fanfic authors interpretation of some of my favorite characters. There's an infatuation at work which doesn't allow for the nuance I see. Thank you - at least now I understand why their stories irritate me so much.