Other people have no reason to group with you though. Everyone is perfectly content doing their own thing and will often outright decline party invites. The only place this was ever not the case was on Mist's daily island.
I would hardly call auto-grouping dumbing down. It's a passive thing that helps put the "Massive Multiplayer" back in MMO, which is something WoW has been lacking outside of capital cities for years now.
They have a reason to group with you for the reasons provided above: quest-item sharing, XP sharing + party bonus, crush quests faster, round-robin looting for non-quest drops, etc.
Forming parties is necessary for optimal play and I never had an issue with forming them. If someone else is in the cave smacking the same quest rats you are, then it was common to send/receive an unsolicited party invite, then split the party as you split ways with a `/wave`.
What about the RPG in MMORPG? It's too easy to relinquish all social decisions from players including the decision to party with someone or not.
But then again, maybe people don't communicate as much in WoW anymore and zone spontaneity is dead and Blizzard removed the LFG (Looking For Group) channel. I haven't played since vanilla WoW. I'm sure the game is much different now that the 1-60 experience isn't part of the game anymore, so we're coming from different places.
I would hardly call auto-grouping dumbing down. It's a passive thing that helps put the "Massive Multiplayer" back in MMO, which is something WoW has been lacking outside of capital cities for years now.