Film is a visual medium. For the first quarter-century of commercial motion pictures, movies did just fine with no dialogue except for occasional brief intertitles (and sometimes not even those).
You ever wonder why no one watches them now????????????????????
You can argue tastes and all that jazz, the reality is the acting is all about dialogue, tone of voice, body language etc.
Acting and developing characters seems to be a pretty big part of film, some might argue that's why there is a thing called the academy awards who knows.
Maybe all the neuroscientists and acting professionals are clueless.
But it is not, as you mentioned, not just about dialog. Body language is nonverbal. Facial expression is nonverbal. There is more to Spock than his dialog, Nimoy's body language helps sell the character. Lifting an eyebrow says as much as the line "fascinating". Silent actors were the masters at acting without words.
By bringing body language into this discussion, you've pretty much sunk your point about dialog.
Absolutely.
80% of all human communication is non-verbal. That's a fact, and it's also why the early users of the internet quickly developed emoticons, because they discovered that people communicating in real-time using solely words on a screen were more likely to mis-read and mis-construe other people's intentions if what they wrote was not being accompanied by some kind of visual 'emotional' indicator. Prior to the internet, the same was true on telephones, where even a person's voice could be mis-read by the person on the other end of the line. There's
nothing to beat genuine face-to-face contact, because it is through these kinds of subtle gestures that we are able to convey our intended meaning, when the words themselves are ambiguous.
As to the idea proposed that we are somehow unable to build character development without dialogue, and that early silent movies are deficient in this area, then I can only assume that people who make this claim have not actually watched a lot of silent movies, or taken the time to actually
absorb into them. Somebody like Mabel Nourmand, for example, was an expert in conveying the emotions by the subtle use of pantomime: with a look at the wedding ring on her finger, a sideways glance at her character's husband, and a rolling of the eyes, she could show us a woman who has endured many trials from her husband over the years; and with not a shred of dialogue required to show that this is a character with a history. If a viewer is unable to decipher a message this simple
without the aid of dialogue, then the addition of spoken dialogue to the scene is hardly going to make a substantive difference to that comprehension.
Even in this day and age, in the 'talkie' era, the basic art of being an actor has not changed: fundamental to their craft is the ability to translate the emotion
behind the words into an understandable form, through the use of gestures and expressions; or for a director to do the same with the scene as a whole. Film/TV/Theatre is
inherently a visual medium.