When I was a kid, I read Hans Andersen’s original version of “The Little Mermaid” (Copenhagen: Reitzel, 1837) and didn’t like it, so I never saw the movie.
It's a beautiful tragedy of unrequited love and self-sacrifice, wouldn't sell well by Disney, king of the happy ending.
Same "happy ending" treatment for the Pied Piper story. Those children were never seen again.