Based on this season's form, and the form of others, you are spot on.
But I think the objective answer is a couple of things, IMO.
i) one, is his price tag, and association with Moyes - it's not fair on Fellaini, but it is what it is. Some will never let it go
ii) his playing style - I think most of us "dream" of United playing brilliant, direct football, and we're comfortable in possession without panicking when pressed. Fellaini seems to be utilised best as a number 10, higher up, which at his very best, causes problems from "long balls". Yeah it's a great plan B to have (like yesterday) but it's not what we should be striving towards. Simply put, he's way too expensive to be an impact sub.
Just as a side note though - I agree with what you said. I don't dislike the guy - but essentially he's not what we need at either DM, CM or AM, IMO.