Seems to me there's folk music and folk music history. Folk clubs were where people took turns to entertain each other. That is the essence which, to my mind, defines whatever genre of music performed as 'folk'. Yes. They booked guest artists as well but that essential element remains.

Pure traditional folk music (ie; when author and origin is lost in the mists of time) worked as folk songs when they were first composed because the issues and themes applied to most of the people likely to hear them. This isn't entirely the case any more. The folk tradition was born of musicians who were singer / songwriters at the time.