What happened to movie trilogies?
It was always exciting to watch the first movie of a trilogy, seeing the world being built up and what that world presented. As the second movie came along, we saw the world expand and we delved deeper with our character and finally the last movie was the conclusion. However, movies no longer use trilogies to tell their story but instead expand to six or more films.
This isn't a bad idea. In some cases more than three movies is necessary such as Harry Potter and Mission Impossible franchise where a continuous story of that world is intriguing. However, the problem with movies that over gamble and release more than three films is a loss of interest in the main protagonist. In the Bourne franchise, the resolution for the third movie was all we need but with the fourth and fifth it lost its emotional connection we had with Jason Bourne. Resulting in two boring flicks.
The reason movies get boring after the third installment is a trilogy acts as a three act structure. With the first movie represented as the setup, the second film is the confrontation and the last installment is the resolution. An example is the Star Wars trilogy with New Hope acting as the setup by setting the rules and introducing the worlds, Empire Strikes Back is the confrontation (literally) with Luke fighting his demons and against Vader, and finally Return of the Jedi was the resolution and closing the book on that story. Until The Force Awakens (which I like) was released in 2015 which lost the emotional connections and tries too hard to rekindle our attachment. The death of Han was the only emotional connection I had with the characters.
The biggest support for trilogies is the experience. Now, with these universe movies they are also experiences but with trilogies the three films watched back to back is more magical because that time we have with out character means we see their development by the end of the last film. While with a six movie franchise, we see the development early on and then we are left with three other movies with our character already blossomed and not flawed, an example is the Die Hard franchise. John McClane becomes a super hero and doesn't do anything wrong and can survive any explosion. As a result It becomes boring and the stakes are lost.
As I have mentioned, franchises such as Harry Potter work with more than one movie because of how many books there are and the complex stories. Imagine a movie being a fat piece of dough and the first movie kneads it, the second movie proves it and the third movie bakes it. What do you get? A perfectly tasty bread. But then take the dough and stretch it for some reason, holes start to appear. Too much stretching is the fourth, fifth and sixth installment, You don't need to stretch it but you do it anyway. Plot holes become more apparent and the bread becomes a mess. That's what happens when a simple story gets the 10 movie treatment. Simple story is better when told in a simple way. Bread is better when baked in a simple way.
But...
Is it a bad idea for trilogies to die away?
I believe that trilogies dying and making way for more expanded movies can lead to exciting films. We are in a new era of cinema which I call the "universe films". Studios are now beginning their own universes that can expand a film's world. It is an exciting time because this change is still in an early phase and will only grow to become better.
In essence the universe building will make cinema exciting again. With trilogies, once it's done, it's done. Audiences crave more from films and want stories to continue. Movies that have more than three films can explore more of the world that was established, Mission Impossible has been going on forever and has continually grown stronger and Fast & Furious has upped their game (for better or worse) and deliver movies the fans want. They have both become better with their latest release.
Without the restriction of three movies, studios can build their movies from the ground up and take as much time to tell a story. It's all about creating an excitement with the audience and a studio slate with a movie universe is more exciting than a movie slate with just three films.
Also...
Movie trilogies dying is an evolution in cinema. We now get franchises that could last a hundred years. Is it a good idea? Maybe or maybe not but it's a necessary step in discovering how far we can take this art form.