I'm going to reverse engineer a concept in order to apply it to writing:
If you think about great moments in cinema.... actually go ahead and do it.... think of some favorite moments.... now, think about the entire sequence of edits which make that moment. Most likely - even if your favorite moment was a big action scene - there was a face in there - responding to some stimulus.
This is how we help the audience understand what is happening.
When the film is being edited, you are watching for opportunities to cut between stimulus and response.
This means - something happens - then someone reacts to that. You can flip this around too. Someone reacts to it, then we see what happened.
When a film is in production, the director is always looking for ways to keep the audience asking questions of the moment. That means, not big questions like "What the hell is this movie about?" - But small questions like - "What would Jack think of this?" The reward, is to see it. Likewise, we might be watching a character's response to something and be thinking "Wow, what is she seeing?"
These moments happen to fast that the question isn't verbalized in the audience's mind, it is a momentary flash. When you can connect to your audience on that level, you've engaged them in your story.
Reactions, though, are a difficult thing to write and they don't have the same impact as on screen because they lack the face that we respond to.
So, instead of writing in the reactions, the writer's job is really to create a situation where these reactions can occur.
This is to say that when writing, you want to think of building your scenes out of moments that generate responses and reactions by the characters.
They can be large moments, but they can also be small moments.
Like in music - you don't want to play the same note for the entire song and you don't want to play the same rhythm or even texture. With your story, you want to build your scene from a variety of reaction-deserving moments and by various characters and in various sizes.
one character shows fear, the other shows.... affection?.... the first character shows suspicion... the other shows.... disappointment... we stay with the second character who transitions into loathing..... the first character returns to fear, but amplified...
Something is happening in that scene between two people!
One of the most common problems I see when reading scrīpts is that a whole scene will go by and it plays one note the whole time.
An actor can't play one note the whole time and create a scene. An actor needs an opportunity to vary their performance in order to be effective. The magic happens in transitions - whether they are from response or an inner change/realization. The audience needs the actors to change during a scene or they will become numb to the note.
This is true of the entire film as well. You want your character to move from state A to state B.
Cinema is all about people responding to eachother and things changing. Perhaps the audience craves this because their lives are mostly one note already and thus movies are entertaining by being a symphony of emotions. Perhaps the audience craves this because they are already a symphony of emotions and the movie helps to conduct this for a while into a cohesive form. In either case, the audience craves it.