This film is commonly misunderstood and disliked these days, but thats only because people don't know why it is the way it is. Rooty Toot Toot, and most of UPA's work, was created with the intent to break from traditional animation and create something more relatable as fine or modern art. Something I think was highly successful. A film only appreciated by those willing to disregard the standards of loony toons and Disney.
The animation is zany and bizarre, the designs are fantastically simplistic. Watch for how the backgrounds only depict the minimum of what is necessary to visually represent what's going on. There's no need for full blown cell coloring here. I think the style matches the jazz perfectly.