There are special interest cruises for singles and other groups. Why not have one for the misanthrope/pessimist cruiser? You could almost guarantee that the food would be bland, the service substandard, the shows boring, the fellow passengers either too old or too young or too wild or too sedate, the decor would be too bright, and the ports of call a waste of time. Of course we would require a ship which is old and rusty, while at the same time totally lacking in nostalgic charm.
That way all these complainers could...well...as the saying goes..."Birds of a feather could flock together" and have sympathetic ears in order to exchange horror stories.