I wouldn't have minded a sung "hallelujah" or even a simple "amen" somewhere in the piece. Heck ... that sort of thing was good enough for Handel, Bach and Beethoven in their "masses".
Then again, none of them guys ever won the Pulitzer Prize, so ....
The audience seemed to like it, by the sound of the applause at the end. (Had this piece been written by Stockhausen, I'd have guessed the applause was written into the work itself.)
It is interesting that I came upon this post and this piece immediately after listening to a recording of the soundtrack of "The Drowning of Lucy Hamilton" by Lydia Lunch and Lucy Hamilton, on which Lunch plays piano and guitar and Hamilton plays the bass clarinet and guitar. I had put on side A forgetting to change my VPI turntable to run at 45 rpm instead of 33 1/3, and so I listened to the entire Side A on the slower speed. But I do like it that way: the bass clarinet is rather haunting in its sound. I mention all this because there seemed a great similarity between the Lunch/Hamilton piece (from 1984) and this voiceless mass. Then again, Lunch and Hamilton never won a Pulitzer Prize either. Alas ....
(For the two or so of you unfamiliar with the Lunch/Hamilton piece, a sample....)
Note - Lucy Hamilton is the working name on this recording for Constance Burg of the band Mars, a rather experimental no-wave "noise" oriented rock band which I love almost as much as I love Lydia Lunch (born Lydia Anne Koch), a true legend of the "noise music" no-wave pre-punk/post-punk/no-punk/all-punk movement from N.Y.City in the 1980s. No Pulitzers, though.
It is interesting that audiences are more receptive to this kind of music that they were a few decades ago.
I attended the Staunton Music Festival a few years ago and there was a standing ovation for a performance of a work of John Cage.