If Walt Disney had animated a Shakespeare play or western epic when he first started out, animation would be treated like what it is, a technique that can be used to tell any kind of story for any kind of audience. But instead he started with a whistling mouse on a steamboat and Grimm's fairy tales, and the animators that came after him followed suit, so that the impression was implanted in the collective American conscious that cartoons are for kids and adults can dabble every once in a while. Saturday Morning is a symptom of that mindset. Getting rid of it doesn't change anything.
From the earliest days of animation, cartoons were shown in movie theaters and meant to entertain audiences of all ages. Look at some of the Fleischer Brothers' cartoons from the early 1930s, especially the early Betty Boops. Those were definitely
not made just for children!
Rather than a symptom, I'd say that Saturday morning is the
cause of the attitude that cartoons are "just for kids."
(And Disney didn't start with Mickey Mouse. The first cartoons he personally produced, directed and animated were the Alice Comedies, a series that blended animation and live action.)