“I know I’m the only person who feels this way in the entire world, but I don’t like the voice they chose for Elsa. I just think the voice is wrong for the character and the face.”
While I think that Idina Meznzel’s voice was serviceable, it isn’t the best match.
This reminds me of the times when traditional animators would model their characters after the voice actors in some way. They didn’t do this for every movie, but it was a way for the animators to better sell the character they were animating. I think that would have helped in Elsa’s case. Because her design is part of the new Disney-ideal princess (i.e., Rapunzel clones), it doesn’t match Menzel’s mature, deeper voice (especially considering that after they heard Idina sing, they changed Elsa’s character around to fit into what it is now rather than her original role as an active antagonist).
I remember looking at the Let It Go scene the second time and critiquing the animation. You’ll notice that, while it is a very serviceable lip-sync, doesn’t quite match the passion and feeling that Menzel’s voice exudes. This kind of goes back to the whole debacle about the “keeping female characters pretty” comment that was made by an animator before the movie was released.
And even the scene where Elsa cries over Anna’s frozen body, her emotions seem held back. I will always compare it to Rapunzel’s face when she thinks that Flynn Rider is dead. Her face is covered with anguish and sorrow; you can feel her emotions.
Now look at Elsa’s:
There i definitely the feeling that the animators were probably told not to deform Elsa’s face that much, in order to keep her pretty.
TLDR: From what I can tell, Elsa’s character design and the fact that the animators seem to be holding back on her emotions is what probably makes Indina Menzel’s voice somewhat ill-fitting for the character.