First let me say I am aware of my own limitations. I can generally sing in tune and use simple guitar accompaniments which match my abilities.
uncritical acceptance of performances in singarounds and clubs results in a downward spiral. The more able performers whose criticism and advice could be the most helpful are the first to find pastures new.
Some months ago I went to a singaround I had not visited before. Of the half dozen other players two were Ok, one forgot the words, one sang way out of tune, one had the words on paper but stopped due to nerves, one nearly played a guitar piece all the notes but order and timing a problem. An old regular at the pub stopped me as I left and said do come back, sometimes people come who can play and sing. Will I go again- doubt it.
Although slightly off the point of the sensibilities of unsought criticism, I think there important issues about performance in any setting which need addressing.
john