What other movies have been based upon that?
People have often said the same thing about other adaptations. A Clockwork Orange was given many of the same criticisms. Language being such a huge theme of the book to even the way it's written yet that culturally significant part of the book is very well represented in the movie by having the rest of the adult world speak normally and even being confused at how Alex speaks.
Lord of the Rings also got the same issues brought up. That there were too many subtle themes and grand plots that in no way could translate to a film yet Peter Jackson turned it into a critically acclaimed franchise that gets praise to this day.
The Shining is often hailed above the book for it's ability to push those claustrophobic and isolation themes beyond what Stephen King could do in his book.
I'm not saying the movie would be better, hell in the wrong hands it could be a disaster. That doesn't mean that nothing in the book is translatable over to a movie.