Watch any bad movie and every scene will often seem completely independent of the other scenes to the point where if you took out the scene, the overall story wouldn’t be hurt because the scene had little to do with the overall story in the first place. Bad movies try to cram in irrelevant scenes just to give the audience what they want to see. In a bad action movie, irrelevant scenes will pile on the action with more explosions, gunfire, and fights. Think of a bad James Bond movie where assailants pop up long enough for James Bond to kill them until more assailants pop up.
In bad comedies, irrelevant scenes try to be funny but in the process, the scene doesn’t help the story. In a 0% Rotten Tomatoes rated movie called “The Layover,” one character traps another in a filthy gas station restroom. Then the woman in the restroom steps in the toilet and falls to the floor, trying to climb out the window. That scene isn’t funny and has nothing to do with the story. It simply tries to be funny and fails miserably. Even worse, it has nothing to do with the story so it’s pointless to begin with.
Scenes only work when they connect and link to other scenes. If you write a scene that has no connection to another scene, what’s the point of that scene at all? Independent scenes are the ones most likely to get cut from a movie anyway.
If you read Quentin Tarantino or James Cameron scripts, you’ll notice that they tend to overwrite their stories and wind up cutting scenes that often repeat information that other scenes already provide. In “Django: Unchained,” there’s a huge backstory about how the hero’s wife was bought as a slave that separated him from Django. Then her owner lost her in a poker game to the villain. Yet all this information is irrelevant because what we really need to know is that the hero’s wife has been separated from him and he wants to get her back.
In “Aliens,” James Cameron wrote a scene describing the first family to find the alien egg (and get the alien wrapped around his face). We don’t need to see the alien attacking one of the first settlers on the planet because we already know how the aliens attack and spread, so this entire scene was irrelevant.
Even in other movies such as “Star Wars,” there are scenes that aren’t needed because they don’t add anything to the story. The early scene in “Star Wars” shows Luke talking with his friend Biggs, who will be joining the military but has plans to join the rebels. This entire scene got cut because knowing anything about Biggs has nothing to do with the rest of the story. You can still see remnants of Biggs near the end when Luke reunites with Biggs and Biggs later gets shot down trying to protect Luke. That reunion scene near the end with Biggs doesn’t make sense because we never met Biggs in the first place. However it’s short so it’s easy to ignore.
When you write scenes, don’t think about making them self-contained, independent entities. Think about making them part of the overall story. If they don’t support the overall story, they probably serve no purpose. Write stories where every scene is necessary. When you do that, you’ll likely avoid writing a bad movie.