There is still plenty of good music to be written in C Major.ACD includes this admonition in a post whose central point (read it for yourself, of course) that composers should be more concerned with writing the most substantial music they can, and not be concerned about being (or finding) the Next Big Thing. His point isn't, I don't think, that composers should write tonal music, but that they should be open to everything that is of musical value.
Most composers I know and that I know of aren't looking for (or to be) the Next Big Thing. Many are looking for a Next Big Idea, but I can't see anything wrong with that,) What most composers are looking for is a way to find their voice, to find a way to say in music what they want to say. A more relevant Schoenberg quote may be this:
Once, in the army, I was asked if I was really the composer Arnold Schoenberg. 'Somebody had to be,' I said, 'and nobody else wanted to, so I took it on, myself.My personal response to Schoenberg's C Major comment is this: no shit. Really, if anybody despairs of hearing new tonal music they aren't looking very hard, or they expect it to be delivered to them automatically. The vast majority of composers, in and out of the academy, write tonal music of some kind or another. They always have and they always will. It's easy to find, even if it doesn't get the most publicity, even though it usually does. You can't demand that the public face of the music world to offer a reflection of your tastes or that the music press feature music that isn't pursuing new ideas. It doesn't work that way in music, or in any other field of human endeavor.
Art is a lamp that sheds light on our lives; it is not a mirror offering us a flattering reflection.Here endeth the lesson.