"In the same way, a person singing at the folk club doesn't have to be a performer ... Performances are for stage, screen and television."

I couldn't disagree more. This attitude is at the root of the problem that this thread is discussing.

I'm not talking about performing in a stage sense, and I agree that style of performance is often not appropriate for folk music. By "performance" I just mean the ability to deliver a song so that people will want to listen to it. If you are going to sing a song to an audience, then that's a performance.

Folk music puts the song itself above the singer. It is not necessary to have a beautiful voice or to be a brilliant accompanist, and these can sometimes get in the way of the song. All that is necessary is to deliver the song effectively, so the audience can enjoy it.

Before you set even out to the folk club, choose a few songs and practice them. Find which pitch suits your voice, think about what the song is about and what you want to get across to the audience, think about phrasing and breathing. For preference, memorise the words (not least because doing so will help you with the other aspects) but if you really cannot then learn to sing from a book effectively, rather than just reading the text.

None of this is difficult, and it is quite separate from matters of vocal technique which is of far less importance in this context. It is simply about preparation. If someone cannot be bothered to learn how to put a song across, why should they expect people to be bothered to listen?