There are plenty of creators (writers, directors, composers, etc) who end up creating work within a existing universe. Think making Star Wars movies, or writing a Star Trek novel. Often the desire for the creator to put their own stamp on the work bumps up against the “rules” and history of the universe. But how should you approach creating something in a universe that already has rules and history?
Some creators are brought in to create works within an existing and defined universe. This includes things like Star Wars, Star Trek, Middle Earth, MCU, etc. This isn’t about a director or producer taking an existing work and bringing it to another medium. Adapting, say, a written piece like a novel or comic book and creating a motion picture or TV series based on it has its own challenges. This is about when someone is tasked with adding new stories to the body of work already in existence. An example was when JJ Abrams was brought in to write the screenplays for Episodes VII, VII, and IX for Star Wars. He was writing new material, but stories based in an already-defined universe.
Let’s face it, all creators want a chance to put their spin on a story, movie, etc. They want a chance to create new things like space ships or monsters. Costume designers want to create their take on clothing, including uniforms. When they are given a wide latitude, you end up with things like the uniforms in Star Trek movies constantly changing, even though militaries don’t alter uniform design nearly that frequently. The Star Trek movies often each feature different opening credits and varying soundtracks.
Star Wars was one universe that, when under control by George Lucas, tended to hew to a certain line when it came to the design of things. The uniforms didn’t change all that much, if at all, between movies. Only a few new starships or other vehicles were added to some movies and the various TV series. The music was very, very consistent, and the opening sequence for movies and TV shows remained virtually unchanged once defined. All that changed when JJ Abrams was first brought in. Sure, some things (like the soundtrack) remained the same, but Disney allowed Abrams to basically obsolete all manner of Star Wars history that was once canon. Presumably this was because he didn’t want it to limit is own creative freedom. The result was 3 movies that were something of a mess (this video has an interesting take on the movies), and invalidation of a significant body of history and canon that had already been built up.
Interestingly, JJ Abrams basically tried to do the same thing with Star Trek. His movies created an alternate timeline, which freed him from the constraints that the Star Trek universe and existing canon would have imposed. The result, though, were movies that felt less and less like Star Trek as they progressed. It’s telling when Wil Wheaton’s comment when the 3rd alternate timeline Trek Movie came out was “gee, look, a science fiction movie with Star Trek uniforms”. It had the nominal appearance of Star Trek, but seemed to be missing the “Star Trek” bits.
My take on working in this kind of situation: view your work as creating a period piece. It’s really not all that different than if you were to create something set in a particular location at some point in the past. For example, if you want to write a novel set during the US Civil War, then you don’t get to have automobiles, telephones, or electricity. Your story will, or should be, constrained by what’s available and what would be “normal” for that time period. There is no Las Vegas, and there is no Nevada yet, so you can’t have a Civil War casino heist story.
Setting a story in a universe that already has history, and where fans have some expectations, imposes very similar types of constraints. Some creators balk at the idea of constraints. But a truly gifted creator would find a way to create something new within the framework of something that already exists. That’s just as creative, if not more creative, versus stating”I want free rein” and ignoring those constraints. And frankly, I think you end up with a better result.