Edward Hanslick (1825-1904), in: Pleasants, ed., Hanslick's Music Criticism (1950).
True, but slightly misplaced. Hanslick may have thought Wagner was a superlative, but he was only the necessary comparative to Schoenberg, who was the true superlative. Taking a tonal center away from a piece as a whole was Wagner's subversion in the Tristan prelude. But taking it away at any and every given moment was the next, logical step. Perhaps another quote is appropriate about Wagner, then.
"Is Wagner a human being at all? Is he not rather a disease? He contaminates everything he touches -- he has made music sick. I postulate this viewpoint: Wagner's art is diseased." Friedrich Nietzsche, Der Fall Wagner (1866).