Several thoughts:

Is the organisational aspect separating amateurs and professionals, as commented on elsewhere?

Are things like H&S and DBS influencing it?

You are part of a Festival organising committee, which means the performers will get to know you, and once they know you, you'll be on the inside circle. It doesn't solve the problem for others, though.

The oldtimers of the 1960s heyday aren't going to be around much longer: old age does not come alone. This could mean the circcuit can no longer carry the overheads, though.

At a personal level, can you separate the music and the people? Even if you dislike the people, you can ignore them for the music. Plenty of performers have, indeed it may be something the inner circle: they don't actually like anyone. We've seen it on certain threads here too!