I've heard this before but a new insight clicked with me today. Sometimes writers try to write something that is popular now. Say if vampire movies are in then they try to write a vampire movie. One problem with this is that by the time they finish the screenplay and it gets produced that cool fad is over. So now you have this script that no one wants.
My new insight today was this idea of writing what is popular is also not a good idea because it's not something uniquely written by you. What makes any script great and what any producer and audience member is looking for is a great script with a clear vision and direction. If you write a story that's in your head that you have to get out then no matter what the story line or genre it is, it will have a through line that is important to you. If it's important to you then it will connect to other people. The plot points won't be cliched and formulaic because they will be unique to you. It'll be a western your way or a Rom Com your way.
The through line is important because it connects everything. A dream can be wild and crazy but emotionally it feels true. That emotional connection is your through line that you get when you must tell that story. When you've got to write about the hunting trip you went on. It's not because oh hunting wilderness movies are cool. It's because you have this story in you. That's why we want and need stories and why we first listened to them around a campfire.
This is another aspect producers are looking for because it's hard to write an original script. What good writing is today is an old story told in a new way. So if you write about what you care most about and feel like you must write then you will do all these things in the process and end up with a killer script that will have a better chance of getting made.