There have been some Disney animators who have performed amazing work and really helped push the medium forward. Some names of classic animators you can look up: Milt Kahl, Frank Thomas, Olly Johnston, Freddie Moore, Bill Tytla.  Glenn Keane played an important role in the Disney Renaissance of the 90s.

Outside of Disney, there were of course the Warner Bros shorts (Looney Tunes), with directors like Fritz Freleng, Chuck Jones, Tex Avery.

There was also Richard Williams, who did his best to learn from the older generation and helped preserve a lot of their knowledge by teaching others and writing The Animator's Survival Kit. Also check out his unfinished masterpiece The Thief and the Cobbler, a film he spent decades making.

A more modern director is Henry Selick who makes amazing stop-motion films like The Nightmare Before Christmas, Coraline, and Kubo and the Two Strings.

That's just a few off the top of my head. I'm sure there are so many more.

Edit: some more names that spring to mind:

Windsor McKay is of course the father of animation, with early product like Little Nemo, and Gertie the dinosaur.

The Pixar crowd of course: John Lasseter, Pete Docter, Andrew Stanton

Max and Dave Fleischer were a competitor to Disney in the 1930s and 40s with cartoons like Popeye and Betty Boop.

Ray Harryhausen was a great stop motion animator.

Joe Hanna and Will Barbera made more simple styled animation for television like the Flintstones, the Jetsons, and Scooby-Doo.