One thing I kind of miss (from DAoC and surely available in many of the older MMOs) is open world huge (zerg) PvE raids. ie. something anyone can join and is more about doing the encounter than who can bring how much DPS and what gear you have.
When I think of it, the exact same formula is what made PvP "accessible" to the crowd. ie. the huge PvP zergs running around in Cyrodiil, while personally I prefer smaller scale PvP, I do recognize that this makes PvP accessible to people that would normally not touch PvP at all.
Same thing happens in these PvE open world raids. I'm not a PvE player, so I have little interest in becoming a Dungeon crawler or Trial runner, but I do like to break up the monotony and being able to join such a zerg PvE raid would do just that.
Examples from DAoC.. the Master Level raids, Darkness Falls raid, Legion, ... 100+ people which no bitching about gear score or class or whatever. Just people having FUN.