Most original material Disney adapted was bleakier and more grisly than the adaptation.
Most of the tales collected by brothers Grimm would today be horror stories. (Did you know that Cinderella's evil stepsisters had their toes and heels cut off so they could fit in the slippers? Or that the ravens pecked their eyes as punishment? Or that Maleficent ends up in a boiling cauldron full of vipers?)
I bet Disney would be able to adapt even something like "Requiem for a Dream" into a happy hero-coming-of-age story.
You lose a lot if the only version of these classics you've seen (or read, or heard) is Disney's sweet & shiny simulacra.