That characters shouldn't say what they're thinking.
That they shouldn't say what they're feeling.
That they shouldn't tell someone what that person already knows, simply because the audience doesn't.
That they shouldn't be telling one another what the scene is about.
That nothing should be there that doesn't have a reason for being there.
That nobody should say something unless he has a reason for saying it.
In real life, people who talk about themselves, their lives, and their problems are boring. Ditto in the movies.
That a scene that doesn't advance the story shouldn't be there.
That simply providing exposition doesn't count as "advancing the story." Advancing the story means introducing a complication or a resolution or laying the groundwork for a future complication or a future resolution. Sometimes scenes can do more than one of these things -- but they've got to at least do one.
Story and Character are simply two ways of talking about the same thing.
NMS