Filmmaking is about everything.
To be a good filmmaker, one must have their tentacles in everything.
This includes the nature of reality.
Objectivity refers to something that can be known; something existing independently of yourself as part of reality.
Subjectivity refers to something which can't be verified or is not a universal experience; something existing only inside your mind.
Now that you can distinguish the two, it's time to apply this to everything:
Why are you really making this movie?
Who is this movie truly for?
Is the your footage actually good enough?
What is your competition genuinely doing that's giving them an edge?
Is your final draft truly entertaining?