I've always considered songwriting to be an independent skill playing music. Some musicians are just so good at writing songs that it almost doesn't matter whether or not they're above average in their musicianship. I don't think anyone would rate Bob Dylan as an exceptional singer or guitarist, but he's unquestionably one of the most prolific musicians of the 20th century. I'm probably an even worse singer and guitarist than Dylan, but if I could write something as good as Like a Rolling Stone, there's no question I would try to perform it myself and have it released before giving the song to someone else.