I won't pass judgment on your reaction. Everyone's experience with a movie is different. But I will say that I flatly reject the idea that "a film needs to have a hero and villain to build tension and to lead to a proper resolution that makes the audience feel what they watched had a purpose." Pretty sure there are plenty of acclaimed movies—from the US or international—that have found audiences and feature characters that are not clearly good or bad. All movies do not have to adhere to the hero myth to work as movies.