A thought occurred to me this morning, a theory that I hope to come back to with more depth, after I've stewed on it a bit. Here's the theory:
I've noticed ripple effects in bad shows. Bad dialogue leads to odd directorial choices which leads to square-peg acting. At some point in the production of a play, something may go wrong. The resultant problems for that production will extend from that initial error. Since traditional play production is a linear affair, you can chart out a hierarchy of problem areas.
Director's take on the material
Rehearsal (Actor's take on the material)
(I know I'm missing steps. This is only a cursory essay of this theory.)
When troubleshooting (or criticizing) a play, one could go through this list step by step to 1) see what each person may have contributed to the final product and 2) discover where things went fundamentally wrong. The deeper the flaw, the less likely you will be able to fix it, but at least you can stop hounding your actors if the script is shit. (I guess if you know the script is bad, you can make the most of it and come out the other end with a pretty entertaining product. I've seen that happen.)
For some productions, the problems will be holistic. For the vast majority of shows, this may be a handy evaluator's tool. It will require further cogitation.