There’s more to it than giluy arayos.
I think what you refer to comes from the unique lav of lo sikrivu ligalos erva, meaning don’t come close to transgressing this sin, as opposed to others where the Torah simply states to do or not to do something.
One issue, for example, is that music has a unique power and it connects to the soul, so to speak. Therefore, one would obviously not want to hear music that was not made and performed by as pure a neshama as possible.
And an issue that concerns both music and movies is that everything we see or hear has an impact on us. So even if the movie (or song) in question does not have a blatant tznius/arayos problem, it’s essentially impossible that the song/movie’s influence will be 100% in keeping with the Torah’s hashkafa, and, therefore, listening/watching it is not a simple thing. IMHO.