"are you suggesting that clubs were wrong to book MacColl and Seeger and Walter Pardon"
Where on earth did you get hat impression?
Guests can be a help to a club, but they also can be a hindrance if they are treated as essential
Why have a club if all you want to do is run a series of expensive concerts.
Guests can give the residents a welcome break, but if you want to learn something from their singing yu can do that far more efficiently by buying their albums.
You can "raise your game" by listening to dead singers as much as from the living
A guest a month is just about the top limit, in my opinion - beyond that, it loses its club status - and even then, if you can't manage without guests you may as well fold your tent and go home.
Thee's nothing more inspiring for a singer than to have to refresh and replenish their own repertoires constantly.
Jim Carroll