With artists I would suggest you simply decline, saying that their style is not what your club is seeking. If they are thick-skinned enough [or just thick enough] to continue submitting discs then have them heard just in case the style has changed, but do not correspond further.

With agents, who should be promoting several acts, I suggest that the letter of decline give examples of the artists which do meet your criteria, and leave it up to them. By all means discuss what you are looking for, but it must be made clear that you are the shopper who knows what you want for dinner, not the one looking for something different to put on the table.

To answer your question though, you are right. Also living in the past is no crime, I see no reason to keep it all for myself.