It's true. Lots of the clubs I remember from when I was performing full-time in the late 1970s are gone. Those that are still around often have much smaller audiences, and you *don't* see a lot of young people, although I expect that acts like Boden and Spiers and Eliza Carthy will draw those in, because they give folk music a younger, fresher feel.
And some of those clubs are much less open to untried singers than they were. My "home" club, Twickenham, often has only three floor spots on a guest night, and most of those go to people they already know from singers' nights or who have been recommended by someone they know.