>>then there's the problem of the organiser who only runs a club so s/he can get an audience, and, even worse, then puts on someone even more dire than them - so they'll sound good by comparison. and some do this on guest nights. <<

My club is in that category.

However, we have never knowingly put somebody on who is not competent, and never ever put somebody on who is genuinly crap, to make the main guest look good. When you have various performers in one night, you are bound to get people where the style of a performer does not suit their taste. That is unavoidable.
There are all levels of performer coming through the club, but all of them are capable of doing a 25 minute spot and more often than not a darn sight more. They also do their best to change their songs on a regular basis.
Neither does the club put the least experienced on first, unless it is better for them. What we try to do is get as much change in style between each performer as possible, so the audience gets a nice evening. Of course that is not always possible but in the main it works.

Market Rasen Folk Club

Unless feedback to me is not honest, I get the impression that the standard for such a young concert venue is very high, with plenty of variety at affordable prices for a very rural village. The object is not to make massive profits, but bring live music to a rural community, that otherwise would be deprived as such.
We get good audiences that range from worst 35 to best 89