'It [abstract expressionism] was the last conceivable thing a painter could do to a canvas, so you did it,' she said. 'Leave it to Americans to write, "The End."'
'I hope that's not what we're doing,' I said.
'I hope very much that it is what you're doing,' she said. 'After all that men have done to the women and children and every other defenseless thing on this planet, it is time that not just every painting, but every piece of music, every statue, every play, every poem and book a man creates, should say only this: "We are much too horrible for this nice place. We give up. We quit. The end!"'
254, emphasis in original.
This is directly on the heals of the protagonist, Rabo Karabekian, telling a few of his war stories to his former lover, Marilee. Just prior to that, she had dressed him down smartly for the part he's played in all the crimes of men--most recently, of course, the second World War.
I'm not sure this will be useful from a substantive point of view, but Vonnegut's book as a whole seems quite preoccupied with the problem with humanism after WWII, which is also, of course, part of the problem abstract expressionism, and later, minimalism, was sorting through. And also of course, this last was also faced with reconciling "the end" with what was clearly now becoming a beginning of something quite different: long-term, stable, violent, global capitalism--the confluence of Vietnam and leisure society.