He was, but it's kind of like Belushi in Animal House. "Was it over when the Germans bombed Pearl Harbor?"
"Germans?"
"Don't worry about it. He's on a roll."
Vonnegut was a nut. As an artsy fartsy type in college, I devoured Slaughterhouse 5 and Cat's Cradle, Breakfast of Champions. The last piece of his I read was Slapstick. This was the novel that made me realize he wasn't deep, he just had a crappy outlook on life. I never bothered with his stuff after that.
I had a similar experience. I can't remember his first book that I read, but I really liked it. Then I read another, and another, and another ... and then I ran into one of his books where the 'hero' - the last man on earth, in his last dying movements, configures his body so that his fingers will 'flip the bird' skyward... That was definitely a 'WTF' moment for me, and I then realized (I'm a slow learner) that all of his books had a godless aspect about them and - although fairly entertaining - were at their root hollow, and without hope. I've never read anything else by this fellow in the past 30+ years.
Its a shame that his talent was wasted.