I suppose I better make some response to TheSnail though I don't have any answers. All I would suggest is that people get out and support their local clubs and if they can help to make the unfriendly ones a bit more welcoming then give it a go. If you don't like a club and don't see any way you can influence it for the better move to another (vote with your feet).
A bigger problem seems to be the lack of younger folk at these clubs. There are apparently plenty to be found at Open Mic sessions (which I know little about) so perhaps we need to change a little with the times and accept that some changes in format may be necessary even though many are very comfortable with what they have. If numbers at a folk club are low and static or are steadily declining then a little self assessment wouldn't go amiss.
Though I may have appeared negative in my comments I that was not my intention. Indeed, I actively promote folk clubs in my local area via a website. It's as a result of doing that, that I can see how little effort some of them make to advertise themselves.
By all means get the famous folkies to promote folk clubs but the clubs need to ensure that they are worthy of it.