It's really apparent when you play through the game with the original voices. Ohtani's Morgana really has this "children's show" mascot voice while Morris's Morgana is incredibly conceited.
Morgana was built around getting a very specific type of voice actor, so it was just a tough situation to emulate. The fact that Morgana probably has the most speaking lines of anyone in the game and that she's constantly commenting on every action the MC does really didn't help. Honestly, for P6, I hope they go back to the disembodied narrator. There was something about that I found charming.