I would say that both sides have quite good arguments.
The old Living Seas ride began with an impressive movie and the hydrolators were a cool idea, they created a feeling of things to come that was quite disappointed. Let's face it, Living Seas fans, the ride after the hydrolators was LAME. You rode in a seacab through a sterile tunnel without any theming whatsoever, for several minutes and the only thing you could see was the aquarium. Nothing happened, no effects etc. It was quite boring and added nothing to the experience you would later have anyways when you watched the aquarium from the observation deck.
I understand that Disney had to change that because despite the beautiful music it had it was by far the most uninteresting ride (after the hydrolators) FW had to offer in those days.
But those who critisize that Nemo doesn't fit into a FW-theming are quite right too. Nemo has nothing to do with the topic of Future World and let's face it Nemo and Friends fans, the ride looks quite cheap. It was a later change and it shows. Several effects are very basic (The jellyfishes) and the entire ride is charming but doesn't tell you anything about the seas.
Could it have been different. I say yes. They could have transformed the ride into a much more interesting experience without tacking on a movie character.
They could have changed the ride into a ride through the different environments of the sea, from the abyssic depths of the deep sea trenches where some of the most bizarre animals in the world live to the coral reefs.
The Anglerfish scene in the Nemo ride shows what could have been done, after the hydrolators you would have entered an area that makes you believe that you are really in deep seas, in the region of eternal darkness and where you finally boarded the seacabs that know looked like minusubs, designed to withstand the enormous pressure of the deep. An entire section could have been filled with confrontations with terryfying yet realistic monsters of the deep. You could have done a kind of scientific 20.000 LutS-journey before you finally entered the Seabase Alpha part of the building.
