Chris Columbus - absolutely the wrong director for the film.
Stephen Chbosky - wrote a horrendous screenplay with terrible dialogue and underdeveloped characters and relationships. I'm an aspiring screenwriter myself and I'm fairly certain that if I were given the same amount of time, resources, etc, that Chbosky had, I could probably turn out much better screenplay that would do justice to the material.
The original Broadway cast - much as I love them, many of their performances simply didn't translate to film. Some came across as too old. I think they should have done the film with a cast of age appropriate fresh faced actorsa and actresses.
"You drank a charm to kill John Proctor's wife! You drank a charm to kill Goody Proctor!" - Betty Parris to Abigail Williams in Arthur Miller's The Crucible