According to Raph Koster’s theory of fun, a game is fun if it has something for us to learn and master. The whole “you must have maxed out your character and know how to do the instance blindfolded before you are allowed to join my group” crowd are effectively saying – only do dungeons once you have completely mastered them. Therefore, are they saying that running dungeons should not be fun?
Really, the whole issue arises because Blizzard apparently made a design decision in the Wrath era to reward people for running dungeons that are well below their level of gear progression (you could be overgeared for a dungeon but the badges were still worth earning). That resulted in maxed out players running content that a gear progression model means they should have moved on from… resulting in very fast, safe (and I would imagine boring) runs. And THAT created an expectation amongst players that all of their runs should be so easy and profitable, so they were less pleased to get teammates at a gear level for which the dungeon would be an actual challenge.
The interesting question for me is why LotRO has less of a problem with this attitude, even though the skirmish mark system also allows players to get rewards for doing trivial content. I’m not going to ascribe this to the magical qualities of a “better community” (although LotRO players on average do seem more mature than the WoW crowd) – more likely it’s because the game is much less based around gear progression.