"4’33”" is an excellent example of how you really need to experience a conceptual piece in order to offer any cogent criticism of it. I didn't dismiss it, but I did consider it a gimmick with a point. Then I actually attended a performance and it was nothing like what I'd imagined. As you say, it couldn't be more different from "silence". It's four minutes and thirty-three seconds of not performing, which is something else entirely.