I kind of disagree with the focus on Disney when many different styles of Western animation existed concurrently with it in the 40's and 50's. For example:

In classical American animation, the animator's hand must not be noticeable. The focus is entirely on the character and in the illusion that it is a living, breathing creature. From a Western animator's perspective, it is NOT praise to say "I noticed how well you animated that scene." That is a statement of failure. It means that the animation drew attention to itself. That is the basic violation of classicist representation in Western art, and of "classical" American animation. John Lasseter puts it clearly when he says he prefers the animation of Frank Thomas to that of Milt Kahl. You can tell a scene animated by Kahl. Thomas's efforts disappear into the performance, like a good actor's. That is THE major difference between Japanese animation theory and Disney."

But later on:

The longer I work in animation, the more I understand and appreciate the work of "classical" American animators. If there is one animator whose skill I wish I had, and whose body of work I wish I could claim as my own, it would be Rod Scribner's. His work, more than any other animator, consistently delights, inspires, and astonishes me. I feel that he inhabits the souls of his characters. They are animated (and drawn) from the inside out. With Japanese animation, I feel I am looking at the outline, the surface of the character. (That is, in fact, how they ARE actually drawn-- outlines first, then filled in with shadows.) There are exceptions, of course.

For anyone who doesn't know, Rod Scribner comes from the WarnerBrothers/Looney Tunes family of animation, and is known for his extremely exaggerated work, so much so that in his heyday under director Bob Clampett, it was easy to tell any scene he did from another animator's. Here's a site with a compilation of his stuff (7th video down; be warned-these scenes were from the 40's and 50's, when racial stereotyping was still a thing [And WWII, during which Scribner was working for Clampett]). This contradicts the criticism against Kahl. Also, the rest of the animator reels are from the same period of Western animation, and all the animators clearly had different styles (especially Scribner and Tyer) the degree of which were expressed depending on who directed them and what studio they were working at (For example, the Donald Duck clips in Emery Hawkins' video are from when he was at Disney, and the rest, with the exception of the black and white commercial, are from when he was working at Lantz and WB. In the same sense, all of Tyer's video is from when he was working at Terrytoons, but any of his other scenes at older studios are practically recognizable in comparison). What I'm getting at is that this all seems to narrow down all Western and Japanese animation to a single school of thought, which I don't think is a good way to approach any medium.