The rain in Spain is mainly declaimed

Through painful experience over many years, I have learnt to avoid any movie with a script written by David Mamet.   Hailed as a great American playwright and screenwriter by many, he appears to have – sadly – a tin ear for human speech and dialogue.   His film characters do not converse or speak as we humans do.  Rather, in some variant of a weird, artificial language I call americantheatrespeak, they declaim:  their words are enunciated clearly and loudly, with neither pauses, nor stumbles, nor mumbles, nor muttering, nor cross-talk, all the while speaking in entire sentences and paragraphs, pre-composed and uttered with a formality that would provoke laughter if you heard anyone actually speak like that.   It is not how we human beings speak, except sometimes in formal settings such as courts of law and important congressional or parliamentary sessions.    After seeing Montgomery Clift, with his pauses and false starts and mid-sentence hesitations and on-the-fly mods, how could anyone think to write movie speech of the stilted, unnatural style of Mamet’s?   In The Misfits, Arthur Miller wrote dialogue for Clift that played to his superb abilities, so we know it is possible for a theatre playwright to write natural-sounding speech for film.   As I said, Mamet must have a tin ear.
I now learn I am not alone in this assessment of Mamet.  Adam Gopnik, in a New Yorker article about Damon Runyon, also notes Mamet’s formal, unnatural, language.   Gopnik, however, admires it, for no compelling reason that I can see.    Perhaps americantheatrespeak works OK on the stage, and people who see a lot of theatre don’t notice it when used on film.  Yet, against that, Clift was New York’s leading theatre actor before he ventured onto film.   But on film this style of speech is a disaster, as Mamet’s 2004 film Spartan demonstrates; no, Virginia, it is not the wooden acting or the unexplained gaps in the plot that make this film unwatchable, but Mamet’s stilted, wooden dialogue.   Ditto for the other scalps on his film pelt:  House of Games, Glengarry Glen Ross, etc.   Someone else seems to be writing (or de-Mametizing) the script of The Unit, although even here (unlike, say, The Wire), people rarely pause, mumble or cross-talk.
POSTSCRIPT:  Thinking some more about this, the issue arises because of what Gopnik calls film’s arch-naturalism.  Concepts that could work perfectly well as theatrical productions often fail on film, as, for example, the black backdrops and absurdism of Derek Jarman’s 1993 film Wittgenstein, which was irritating in the extreme.   We have a problem suspending disbelief for film, a problem we don’t usually have for the theatre.   Perhaps the cause, as some film theorists have noted, is that films are akin to dreams, and dreams don’t require us (at least, not consciously) to do work ourselves to imagine whatever is missing from the production.  We are happy to do this work when watching theatre (and when reading books and listening to the radio), but are less so for watching films or TV.
Reference:
Adam Gopnik [2009]:  “Talk it up:  Damon Runyon’s guys and dolls.”  The New Yorker, 2 March 2009, pp. 66-71.