I’m not really into sci-fi, but I enjoyed that one, and when I found the video it still seemed fresh, although odd that the aliens just seem like humans as well. I hadn’t known that it was intended to be staged. I don’t know if audiences would be willing to sit and look at specks of light while they’re hearing the voices.
My guess is that people would be so tickled by the dialog that they wouldn’t mind the lack of visual stimulation – or so it was hoped.
Alternatively, the performers may have reasoned that it was better to let the audience imagine the forms of these incomprehensible non-meat-based entities, rather than present something limiting and unconvincing.