I remember first reading the books as a kid and wondering why it was never made into a cartoon. When I heard of this project and who was involved I got interested. Too bad for me.
It seems the producers didn't realize that just because you're making an animated movie based on a series of books that came out in the 80s doesn't mean you have to use outdated animation techniques and styles from that same decade. Did they blow their whole budget on the (for the most part, horribly performed) voice actors or were they just incompetent? The animation was horrendous--it wasn't just bad here and there, but was terrible throughout.
There's no reason someone, at some point during the movie's production, couldn't have realized just how horrible the final product would be. I felt ashamed on the producers' behalf for having watched it, so I can only imagine how anyone with their name attached to the project must feel.