I've actually had only one bad experience with the duty finder myself. Every other dungeon and boss I've done has been with great people who were either willing to learn or teach, and stuck with things until we got them right.

The difference is most people complaining are having bad experiences with the endgame dungeons, because people are farming them and want perfection every time for their own efficiency. Those doing the lower level ones are doing so for the story or to see what's out there, or just for fun, and are thereby either more relaxed or simply need a victory instead of perfection.