The more time I spend with screenplays and screenwriters, the more I realize how many problems are tied up with a single problem: writers don't know their audience. I'm dealing with a script right now that very generously lets me know when I've come upon the inciting incident and the tragically flawed hero by indicating that directly in the script. He's also included a list of characters, scene breakdowns, and a three-page synopsis. He's got extensive action lines to give me all the backstory and drama, and, just to make sure we're up on all the details, has the characters remind us who they are, why they're here, and what the essential conflict is at the moment in their dialogue. Then there are the flashbacks, the flash forwards, and the montages so we understand the historical context.
The problem is that a movie audience doesn't have access to his copious notes of back-story, character motivation, and survey of the historical period in question.
You can't SEE the movie, because you're too busy reading the story.
A screenplay isn't a novel, of course. And screenplay readers aren't novel readers, either. In fact, they aren't big fans of reading at all. A studio reader may read 6-8 scripts a day, and is responsible for producing detailed notes and making an initial decision on the viability of a script. That's hundreds and hundreds of pages every night. How do they do this?
Basically, they watch the movie. They play out the visuals, the actions, and the set ups in their heads. The last thing they want is someone telling them what's there, or what it's supposed to mean. This just slows them down. They want to see it for themselves. If you need to explain a plot beat, it isn't going to work on screen. A good script reads quickly.
Now, how does a reader keep all the plot beats straight in his or her head? Think back to the discussion of three-act structure. A reader looks for the inciting event, and the second act complication, midpoint, etc. Everyone has their own way of looking at this stuff, and different ways of interpreting the material, of course. But there is a basic way that movie audiences watch a movie. There is a huge set of expectations that we all share. The studio reader simply applies that set of expectations, and measures your script against them.
It's ruthless. It's unfair much of the time. But a good reader doesn't measure how close you are to hitting that perfect formula. She's much more interested in how you exploit those expectations to tell us a good story.
It's stressful giving up action lines and dialogue that tell the reader directly what's going on. But when you start using action lines to SHOW the story -- to bring it to life in front of your audience -- you'll never look back.