You don't have to be a good singer any more if you can rap well.
You don't have to be a good musician if you've got certain computer skills.
To write a good song, an artist has to drawn from reality. There has to be some spark from realism that communicates a real feeling to someone else. You have to be real. Or you have to be a really good storyteller.
Any song I don't feel good about, I shelve. Anything you ever hear me sing, it's because I want to.