"...If you're going for an original story. You're not going to get it this time. The plot is literally the inverse of the first film...Is there any grand message to this film? Any overarching truth to be learned? Not a chance. Still it beats out even most Marvel films for enjoyment, if for no other reason than it never pretends to be "live action.""
If anything, this film shows us who the real star of the series is. There would have to be some major work done to incorporate Marlin as essential at this point. I am not sure Nemo ever mattered less.