In some ways it's less an argument about Kahl than about his usefulness as an example for other animators. Barrier and some of the commenters feel that it's not helpful to hold Kahl up as the perfect animator (Michael Sporn suggests in comments that some of this comes from Richard Williams, who saw Kahl and Milt Babbitt as the ideal animators). His pursuit of perfect drawings -- and his drawing ability was astounding -- may have come at the expense of some of the emotion that could be conveyed by the work of less accomplished draughtsmen.
From this point of view -- and I'm not saying I agree with it; I'm not really familiar enough with Kahl's style to judge him one way or the other -- he's neither the "animation Michelangelo" or the "animation Raphael," but the animation Andrea Del Sarto, from Browning's poem about the technically flawless painter whose work didn't have the depth of Michelangelo's or Raphael's:
And indeed the arm is wrong.
I hardly dare . . . yet, only you to see,
Give the chalk here--quick, thus, the line should go!
Ay, but the soul! he's Rafael! rub it out!
Still, all I care for, if he spoke the truth,
(What he? why, who but Michel Agnolo?
Do you forget already words like those?)
On the other hand, Thad K points out in the same comment section that some of Kahl's best work was in slapstick comedy, something he didn't get a chance to do very often in the later films.
One thing I definitely don't agree with is Barrier's opinion that Kahl's re-design and re-thinking of Pinocchio was one of Disney's "most unfortunate decisions." That decision pretty much saved the movie as far as I'm concerned. The only way to avoid making this story a mean-spirited piece of 19th-century moralizing -- it's one of the many 19th-century children's stories where we're supposed to enjoy seeing "naughty boys" put through gruesome torture -- was to make Pinocchio a good boy, who experiences these punishments for doing the things that even good kids do in moments of weakness (fibbing, playing hooky). It changed the tone of the story from "look what happens to naughty children" to "look what happens to all of us." Kahl's redesign was the way to make this story relevant and relatable for a 20th century audience, instead of a Victorian lecture.