Kat,
The label singer/songwriter covers a large coterie of performers. There are some excellent, inspiring writers who also happen to sing the songs they write. Some of them are listed above.
There is another group often described as young people singing their diary. The content of much of their writing is from personal experience. That is not so bad if the song is able to expand it to a general experience. This is where many fall short. The songs sound like the writer believes you are desparately interested in their everyday life.
U. Utah Phillips (the golden voice of the great Southwest) described these songs in this manner: The generic words say: "I am a poor boy (pain, pain, pain), travelling this wide world (pain, pain, pain), facing the world on my own (agony, agony, agony), just me and my guitar (pain, pain, pain), and I want to get laid."
The recent folk boom has led to more quantity than quality. The unfortunate fact is that talent does not necessarily insure success and, also, is not required for success. Success as a performer requires other business and planning skills that many performers do not possess or develop.
The end result is some true "no talents" amongst the crew and they are invariably the singer/songwriters not the interpreters of the "old" music.
Roger in Baltimore