Movies often use expository dialogue to set up the world of a film so the audience is oriented and understands the "rules." Think back to the cafe scene with Leonardo DiCaprio and Ellen Page in Inception when Leo's character explains the world of dreams to Page's character.
Exposition is also heavily used in sci-fi films to help explain complex ideas. Think about the worm hole explanatory scene in Interstellar.
Or the rabbit hole scene in The Matrix.
Expository dialogue is sometimes necessary to inform the audience and to move the plot forward. When it is done well, viewers will hardly notice. When it is done poorly, the results can be groan-inducing.
But can information be conveyed to the audience by relying more on visuals than explanatory dialogue? Absolutely. In fact, as you work on your own films, I would encourage you to strip away as much of the dialogue as you can and focus more on visual storytelling. After all, film is a visual medium.
This is why I love Christopher Nolan's latest film Dunkirk. It's the perfect example of how to do visual storytelling right. There is very little dialogue throughout the film, and yet so much is conveyed about character, motivations, and emotions. The film feels very economic. There's no wasted screen time.
Consider the opening scene (*Minor spoilers ahead for the very first sequence in the film)
The opening live-action shot is an empty street in a small town. Everything is still. No one is out, except for a few soldiers who are walking down the middle of the road with full gear. Papers flutter gently down all around them. One soldier takes one and looks at it. He sees this:
Instantly we the audience understand the situation perfectly. Rather than use up valuable screen time with a group of soldiers sitting around talking about what's going on in the war, lamenting about the fact that they're surrounded and stranded on a beach, Nolan gives us everything we need to know in one insert. Here's the scene in its entirety:
So, take a second look at the script you're working on. Do you have drawn out scenes of people talking? Is the purpose of their conversation to give the audience explanatory information about the plot, the situation, or the world of the film? If so, consider leaner, more economical, visual ways to communicate the same information.
And if you haven't seen it yet, go see Dunkirk.