The question can’t be answered in a way which lies on the extreme ends of the YES-NO polarity. May be somewhere in between which requires the filmmaker uses his own creative senses, his ability to allow and maintain the effect of flexibility in his cinematic vision without diluting it, his experimentative attitude which allows him to collate a new vision with the existing one and off-course which doesn’t poison the spirit of the movie. Though the director would be free to an extent to create a specific attitude to the narrative but it would not be appropriate or ethical for him to subvert the script merely to make a recognizably personal impacts. The scope and intensity of his creative liberty should be directed towards intensifying the effect which is implicit in the shape of the narrative.
The creative liberty:
The director is responsible to govern all the action in the movie but it should be understandable that this contribution should not be obvious.