With some movies, for example the Star Wars movies there is so much to take in, and it moves so fast that it can be overwhelming for people who need more time to process. It also makes a difference how familiar you are with the previous SW movies as frame a of reference can make a big difference.

Also everyone process information differently, and it has nothing to do with IQ. I can remember faces and voices quite well, but with some people I have a very hard time remembering the name that goes with that face or voice. A few times it has left me in very awkward situations where people clearly know me and I know I know them, but putting a name to them or remembering how/where I know them doesn't come to me.

It doesn't mean I'm not smart (as I am relatively intelligent in many area) it just has to do with memory formation.

Also there are many kinds of intelligence, a person can have a great aptitude in one area and struggle in others. For example a math genius may struggle with reading issues.