I am going to attack this question as a reader, and not as a writer, seeing as I have yet to write satire, and have read many screenplay attempts at satire.
If movies are a genre medium... where does satire fall?
Satire is a genre in literature. However, it is not in film.
I believe there are two reasons for this.
1) Readers have a hard time dealing with satire.
Is this supposed to be funny? Is this supposed to be dramatic? What is it? Because a script is not a final piece of work, a reader will often assume that something confusing is the writer's fault.
In literature, the author is given much more freedom. A reader will assume that the author knows what he is doing and go back and try to figure out the meaning behind confusing passages.
And honestly, the biggest reason is...
2) Most people do not know what satire is.
The majority of scripts I read that have any shot at being a satire are in 99% majority, parody.
For me, the biggest difference between the two are that satire depicts real situations that are true to life. Upon further inspection, there may be nothing funny about satire at all. Satire is a visual definition of cognitive dissonance.
Parody points out how absurd a situation is. Satire is just an absurd situation.