A play is much more than a work of words. It is costumes, sets, lighting, actions and reactions from other players, makeup, voice, and the actors themselves.
If you believe what you say, then you must also hold that Shakespeare's plays are lost to us, for all the original "costumes, sets, lighting, actions and reactions from other players, makeup, voice, and the actors themselves" perished hundreds of years ago. All that have survived are the bodies of words -- which are what people other than you commonly call "plays."
It follows from your view that if Shakespeare had said, upon setting down his pen, "I have written a play," he would have been speaking falsely, since what is written is, on your view, not a play, but only part of one. On your view, anyone who says, "I am reading a play" is speaking falsely, for the same reason.
Your view has such transparently absurd consequences that I doubt that you even mean what you say.
If English teachers want to teach Shakespeare then I think the best way to do it, short of attending a performance, is to show a teleplay.
They should "teach the plays" by having the students watch performances and not read the plays? That would be a fine way to raise a generation of illiterates -- people to whom the writings of Shakespeare would be as silent and meaningless as the pages of Mozart's scores are to non-musicians; people who would know of Shakespeare only what was in this or that performance, and not what was in the play that Shakespeare wrote; people who claim to know Shakespeare but who have never read him, and, in all likelihood, would have no interest in ever doing so. That is not "teaching Shakespeare's plays," Jason, and certainly not teaching people to read Shakespeare's plays; that is teaching people to watch performances of Shakespeare's plays -- and making them as passive and powerless as most people today are in relation to music.
I think it's unfair to divorce an artist from his or her medium and frankly, playwrights are the only artists we do this to. No wonder they so often drink themselves to death! A great or even good actor can add nuance to the words to convey far more than they say on the page and a proper director can elicit subtext not immediately apparent in the script itself. Certainly the script is the foundation, but it is not the whole work as imagined by the artist.
There is no "divorce"! Unless the playwright happens also to be a director or an actor (as Shakespeare was, but we are talking about him in his capacity of playwright), he has ABSOLUTELY NO PART in what becomes of his writings on stage. He writes the words to be spoken, the stage directions, and so forth; beyond that, unless he happens to have a part in a production, the play is out of his hands. It is ridiculous to say that what the performers do with what he has written is
his medium. It's
their medium! That is why we call them performers and him a writer.
An actor can add all sorts of things, good or bad, to what the playwright has written. The writer may like them or dislike them, but they are the actor's work, not the writer's. Actors can miss things, too, or be able to make something of one detail only at the expense of neglecting another. That is one reason why one has to read the play to know what is in the play.
I don't understand why anyone would want to defend such a perverse position. Nobody is denying that plays are, in general, written to be performed, or that to appreciate a well-written play you have to see it performed -- at least, I am not denying any such thing. But
you are denying that to appreciate a well-written play, one has to
read it. To justify this bizarre denial, you make the even more bizarre claim that the playwright's medium is the performance that
he does not create or control rather than the text that he does create and control.
I can understand how some people might advance a bizarre idea just for the thrill of provoking others to defend common sense, but I would not expect anything so frivolous of you, Jason.