What you described are unspecified concerts where anything goes on
A far cry from venues which were set up to listen to and perform folk song
There is no guarantee of hearing a folk song at any of those venues - nor can there be expected to be
Festivals are for the already initiated and they tend to be somewhat "in" affairs - and even they are disappearing - go count the number of major festivals that no longer take place

If you van't describe a folk song I'm afraid that it means you don't know what one is yourself - I think that makes my point perfectly
I went to Swinton many years ago and listened to folk songs - from the sound of it, I am no longer guaranteed to be able to do that now

"Some folk clubs did, rightly or wrongly, generate a poor image"
I can't remember any that presented a poorer one than the one you describe - one where I'm neither guaranteed folk songs or a reasonable standard or, in some cases, haven't even bothered learning them
Jim