There definitely is a difference between someone directing the line at a restaurant and an actor in a house—namely that actors shout, yell, etc to startle people which, in turn, expells droplets with far more force—potentially spreading the virus further. (I believe I read minimum of 10 feet for singing? Shouting/yelling would be further.)
That said, as per your larger thought, I totally agree with you. I do think it can be done safely with the addition of plexiglass and distance, the removal of hanging scenic, and pulsing groups to facilitate social distancing—it is totally a matter of money at the end of the day.