Making dungeons easier was one of the biggest mistakes WoW ever made.
It took something that was a fun, challenging, social activity and turned it into just another way to grind.
Players became impatient. They stopped caring about threat and strategy and only cared about speed and topping the dps meters.
The whole thing became a shambles and the general lack of order caused players to get quite irritable, especially the tanks.
You ended up resenting the people you were playing with because instead of working together towards a common goal, it felt as though we were constantly fighting with each other. Tanks would fight damage dealers for aggro, damage dealers would fight each other for the top spot, healers would fight everybody when the whole sorry mess blew up and suddenly it was their fault that everybody died (yes, it's possible to die in easy dungeons. People get careless).