Of all the classes I took in film school, none were discussed with more direct disdain by fellow students than film theory courses. It's just talking about movies you say, but in actuality, it's a set of criteria established to define how we approach varying aspects cinema and how time has made such criteria more relevant. In a largely opinionated and biased way, film theory reinforces rules, genres, theme structures, etc. that make the movies the 'artform' that it is.
It may not be an easy pill to swallow, but the truth is (film students) you need to know this stuff whether you get it from a professor, the library, or the video store.
I was never one to do exactly what I was told, especially in film school, but I was still perceptive enough to know that challenging myself was the only way I was going to get better at what I was doing. Film theory, however, was still a hassle to me because I was so determined to make my own work that I wasn't interested in breaking down anyone else's movie. What I failed to initially realize, was that despite my lackluster interest in the classroom, I was actually educating myself on filmmaking theories by watching tons of old movies. As a film student - any serious interest in films outside of your lifespan is to be commended.
Yes, there is a difference between theory and history, but by simply acknowledging the work of Chaplin, early Scorsese, early Spielberg, Wilder, Kazan, and Capra (to name a very select few) I was actually teaching myself a lot about the basics of how to construct a story in numerous styles. My point being that there are numerous routes to the same goal (something reinforced over and over again in film).
A filmmaker without knowledge of film theory is essentially mimicking a style that they've seen somewhere, trying to copy someone else's pattern to create comedy or drama. This is because they don't understand that there's a framework that gives meaning to the images they've chosen to showcase. This is both incredibly basic and complex, and can include everything from editing style to the significance of the music chosen, a historical or regional context, and so on. It's not that you can't figure some of these things out by experimenting, it's just that you're wasting your own time trying to discover a formula that countless others have been trying to share with you.
In a simple example, it's the way a relationship can be created by just combining two images together. A shot of a face followed by a shot of an apple could be suggesting that the subject is hungry or has an interest in picking that apple up. Simple things like this help to explain why many student films are so wooden or overly didactic. It's an art to learn how to subtlety convey meaning while naturally encouraging an audiences emotional response.
For instance, we don't necessarily need to create a complex shot by shot of a character establishing that he's hungry. Maybe we just need to hear his stomach growl. Why? A stomach growl is a universally recognized sound conveying hunger. Numerous layers can be added to this to establish context and meaning. Theory, for better or worse, is about heavy and repetitive discussions like this that aim to tap you into the culture and influence of the medium.
Relevance is also the essence of film theory; understanding what your work as a complete unit is saying about society and from what perspective it's doing so. From here we can break down scenes, dialogue, style, etc. Lot's of things will overlap.
Think closely about this, as whether you'd like to believe it or not every movie ever created does actually fit into some category or form of classification. What are you trying to say with your work? What does it mean? Why did you do it that way? None of these answers are as simple as they first seem.