The main problem is not really the players. It's the game itself. By making most of content relatively easy and, most of all, rushable, players don't know how to play anymore. Just put something a little more tricky and it's a catastrophe.
People don't bother to think anymore in this game so the game doesn't really require them to think.

It's even worse today when I see new players that are learning how to play the game and have already all the bad habits of the oldest veterans... and nothing will repair that.
Players also, as stated above, don't have anymore the party state of mind. Maybe only 10% of the players I met say hello when the instance starts and goodbye when it ends. It's the bare minimum...

What I mean is that the game changed the players and now it's too late.