A good reader will find many such 'oblique' and/or direct parallels to other works while a good viewer will clearly see how the faulty script of the film lets the book down.
The problems with the script of the movie are many. The main issue is that though it does stick to one storyline, it fails to build up tension. It fails to rise up to and thus end in a crescendo. The film instead goes out with a whimper.
Thus, if Rushdie was anyways taking creative liberties with the book, he could have taken more, to bring out the essence of the story, the various metaphors while at the same time making it more engaging and 'entertaining' by building the tension to unbearable proportions till the final release.