Using your imagination is important, especially as a filmmaker. Sometimes you can go a while without using it, and then when you have to, you’re stumped for ideas.
I think that’s important to keep testing your imaginations as it helps you keep developing ideas, and coming up with new and inventive methods. This is especially useful in the idea development stage of filmmaking. If you think of one idea then stick with it, it will never develop for the better or change. By using your imagination, your story or ideas will constantly change and develop, making better and more in depth stories and ideas.
Looking back at ideas and constantly developing them makes sure you use your imagination and creativity.