I don't beleive there is a folk club decline.

Most folk clubs, support people to song and play. Very often, having a guest on is not what folk clubs want, as they want to do singarounds.

Consequently, people who go along to sing or play, do not necessarily want to listen to a guest unless they are really good.

If a folk club puts a guest on, they owe it to the paying public to put only the best support acts on. Anything less than that will stop the future audience coming along in the future. They do not want to listen to people who are unable to sing or play.