I can only speak from my own experience.
I have had some great nights in folk clubs over the last year,admittedly I was guesting they were not singers nights.
I have also had frustrating nights at Irish Sessions[last night was an example]where a female guitarist was attempting to accompany a fiddler, and hadnt realised the fiddler had changed key on the second tune, and carried on regardless,[avoidable if accompanists would listen and play quietly if not sure].
Where musicians are not listening to each other and speed the original musician up.,again it is courtesy to let the original musician dictate speed and style
to be fair,I have not encountered that sort of thing in Folk clubs, at Stockton folk club the musicians all play along at the beginning of the night, and seemed pretty together.
on the question of crib sheets, personally, I would rather not perform than use them, but I did hear one singer give a surprisingly good version of The Whitby Whaler from a crib sheet.
workshops of the kind run by Lewes[sat] Folk Club, give people the opportunity to learn and improve, and that benefits the whole of the Folk Scene.
I would like to see more tuition available on a national basis[not just from Comhaltas,because, their remit is solely Irish Music]
if there was a national organisation offering tuition on a national basis,in English/Scottish/Welsh traditional Song/tunes,that[imo] would be useful.