It's interesting to me how passive Disney's main characters often are. That flies in the face of the current wisdom about "the hero's journey," where the main character is confronted by obstacles that he or she has to overcome. In many Disney films, the main characters don't do a lot to help themselves. Often, they react to what's happening to them, but there's no goal that they're trying to achieve.
What Disney features do, and do well, is create interesting supporting characters who are the ones who drive the plot forward. Dumbo's an outcast, but it's Timothy who becomes a surrogate parent and tries to find a place for Dumbo within the circus world. Mowgli is content in the jungle, but it's Bagheera and Baloo who take charge of him to prevent him from becoming Shere Khan's victim. I haven't watched Sleeping Beauty in years, but does Aurora do anything to improve her situation or is it her three guardian fairies who drive the plot forward?
Main characters should have character arcs. They end up in a different place from where they start; the events of the story force them to grow. Supporting characters don't need arcs; they get by purely on the strength of their personalities. Because they're free from having to change, they can be eccentric or mannered so long as they're entertaining.
If you look at Disney films from the standpoint of character arcs, you realize that the main characters aren't necessarily who you think they are. Snow White's main character is Grumpy. Peter Pan's main character is Wendy, though she's hardly central to Disney's version. One of the problems with Alice in Wonderland is that Alice has no arc and neither does anybody else. The same might be true for Sleeping Beauty and Robin Hood. Stuff happens, but do any of the characters grow?
The danger is that supporting characters run away with the movie. You can point to supporting characters who have more personality and audience appeal than main characters. The dwarfs are more interesting than Snow White. Everybody is more interesting than Alice in Alice in Wonderland and Wart in The Sword and the Stone.
In fact, all the Reitherman films suffer from weak character arcs and have supporting characters dominating the action. Without a strong narrative drive, the animators during the Reitherman years indulged in personality for its own sake. Certainly there are great bits of animation there, but they exist in a story vacuum.
In the early Disney features, the main characters were often passive, but the films always generated enough sympathy for them that the supporting characters had a focus. In the '50's and '60's, the studio was less concerned with generating sympathy but didn't always compensate for it by making the main characters more active. Instead, the studio was seduced by the entertainment value of its supporting characters, but without them having sympathetic or active leads to support, the films became collections of vaudeville bits, entertaining in themselves, but not as satisfying.
Rather than have straight leads supported by comic relief, which was the way things used to be done, now the leads are comedians themselves. We've got Mike Myers and Eddie Murphy in Shrek, Albert Brooks in Finding Nemo, Billy Crystal and John Goodman in Monsters, Inc, Ray Romano, John Leguizamo and Denis Leary in Ice Age and Zach Braff and Garry Marshall in Chicken Little. The new paradigm is that it's easier to graft a character arc onto a quirky supporting character than to take a straight lead with an arc and make the character quirky. The supporting character mentality has essentially taken over the films.