Fight Scenes Are Boring
Yes, that's right, I said "fight scenes are boring" and I meant it. Fistfights are boring, gunfights are boring, entire armies warring is boring. Why? I can only answer that after you've been educated...
Thought experiment time!
Bruce Willis is on the roof of a 10 story building. There is one set of stairs. No elevator. No fire escape. There is a bomb in the basement that will go off in 60 seconds. If Bruce doesn't get down the stairs and out of the building in 60 seconds he will die.
Why? The short answer: your brain is being asked to predict the answer to a close-ended question and that causes it to shut down.
Stories only move forward on questions. At all times in any story the reader wants to know the answer to at least one question. Ususally more than one. The question may be, "Will the hero save the galaxy?" or may be, "Is the main character ever going to figure out what she wants in life?" but either way there must always be something the reader is sticking around to learn the answer to. Once every question has been answered, the story is over.
In our example, the question is, "Can Bruce run down all 10 flights of stairs in 60 seconds?" The answer to that question is either "yes" or "no." There is not a third option. It takes less than a second for your brain to process this implied question and realize that the answer is either "yes" or "no." In fact, considering Bruce is the star and we're only 45 minutes into a 120 minute film, your brain knows it can pretty much eliminate the "no" answer and is left just with "yes." Then, having fully explored all the possibilities, your brain congratulates itself on a job well done and considers taking a nap.
The writer of this screenplay was aiming for excitement, instead s/he turned your brain off, which is the opposite of excitement.
Let's try this again, a little different this time.
Bruce Willis is on the roof of a 10 story building. There is one set of stairs. No elevator. No fire escape. There is a bomb in the basement that will go off in 60 seconds. If Bruce doesn't get down the stairs and out of the building in 60 seconds he will die. Also, there's a dozen terrorists with machine guns on the stairwell in-between the 8th and 9th floors and they are all willing to die in order to kill Bruce, who, unfortunately, has no weapon.
No longer borning.
Why? The short answer: your brain is being asked to predict the answer to an open-eneded question for which there is no obvious solution.
Okay... he's going to climb down the fire escape... oh no, wait, it's already been established that there's no fire escape. Alright then... he's going to charge the terrorists and and hope to frighten... no that doesn't make any sense. Can he... maybe it's a masonry building and he can sorta rock climb down using the bricks as toe and finger holds? Hm, that'd probably take more than 60 seconds. Uh... he doesn't happen to carry a parachute around with him everywhere he goes, does he?
What's happening here is that your brain is frantically working, attempting to find a solution. Your neurons are firing at a high rate. From a scientific perspective, this is what excitement is - a whole lotta neurons firing.
So back to the original question: why are fight scenes boring? Because they are centered around a close-ended question, and that question is, "Will guy A win the fight or will guy B win the fight?" In order to make it exciting, the writer has to establish that the main character, the one we are rooting for, is at such a severe disadvantage that he has no way to win. If the writer has established that the foe in question is the best swordfighter in the entire empire, and the hero has never held a sword before, then the hero has no way to win. The question then shifts from the closed-ended "Will he win the fight?" to the open-ended "How will he win the fight?"
Seriously, now I want to know - how will he win the fight?