I think some of the problems mentioned come from a distorted perspective of the song. We all have personal criteria for what songs we want to sing, and choose accordingly. I believe some singer/sonwriters short-circuit their normal criteria when it's a song they wrote themselves. In other words, if someone else had written a poor song, they would instantly know to let it die a natural death. But when they write one themselves, it may not be possible to "see with the same eyes" one normally uses to evaluate songs. "Oh would a gift the giftie gie us, to see ourselves as others see us." (Or something like that--Robert Burns, I believe.)