This past weekend, I took in a bad play and a bad movie. No one intends to make a bad play or bad movie, and I should say at the outset that I don't begrudge the theatre or movie artists one bit. I understand how impossible it is to make a play or movie, and I am certain the folks involved in both were very earnest in their attempts to entertain.
My experience coming out of the play was very different from my experience coming out of the movie, and it raised the question for me: why are bad plays so much worse then bad movies?
For starters, you can't fix a stage play in post. You can't ADR or do reshoots. If you eff up on stage, it's done.
Granted, in the theatre you do have multiple "takes" to get it right, to explore other subtle possibilities, and to react directly off the audience feedback loop. If you're the master of what you're doing, you can make the micro-adjustments necessary to hook an audience and reel them in. Friday night's "dead kitten speech" may require more vehemence than Saturday night's version of the same monologue, based on how awake the audience is. The actor with that uncanny third-eye fixed on the audience can make the adjustment whilst in the moment. Film actors can't do that.
This moment-to-moment connection with the audience is the problem, and what makes a bad play worse than a bad movie.
In live theatre, there is no physical barrier between audience and actor. And so the audience develops a stronger identification with the actors (or at least they can). A dropped line or messed up cue transfers a tremendous amount of stress to the audience in the theatre. There is physical detachment in the cinema, and I would argue that although the connection between audience and actor suffers as a result, that relationship is far more forgiving of gaffes.
These two aspects taken together -- the technical and the psychological -- is what makes a bad play worse than a bad movie.