Sunset Boulevard is a movie that cannot easily be labeled, which is part of what makes it so good. As reality and fiction blur, the audience starts feeling the slight suffocation so present throughout the movie... and find that they are unable to break away from it. Enjoy!

Sources:

https://www.gradesaver.com/sunset-boulevard/study-guide/is-sunset-boulevard-really-a-film-noir

https://en.wikipedia.org/wiki/Sunset_Boulevard_(film)#Contemporary

Credit for the theme song:

Hot Swing by Kevin MacLeod

Link: https://incompetech.filmmusic.io/song/3885-hot-swing/

License: http://creativecommons.org/licenses/by/4.0/