I have a friend who said once that many good rock bands have foundered on the need to write their own material. There is some truth in that. There are good, even excellent, musicians who aren't great songwriters, and know it, but the market urge for novelty can leave them behind in favour of somebody who makes up in nerve what they lack in talent. Is that too cruel? Another friend also pointed out that although many singer/songwriters like to think that they are expanding the boundaries of song form they mostly fall into very similar patterns. I would go on from that and suggest, devil's advocate like, that the more knowledgable ones who can see the patterns are the ones who then change the patterns and create new forms. For every good songwriter there are hundreds of mediocre to lousy ones who are mimicking the good stuff. If it gives them pleasure that's fine, I'll just pay little attention until something catches my interest.