Just like Magnetite2 said, the grind takes its price but it isn't about the grind, not for me it wasn't, it was about cost:value of time spent.
You see, as long as you are in a good company, who cares about what's actually happening? The problem starts when your friends starts to vanish, it's like reverse facebook effect, no one that you know is there so why bother, I'll explain:
when the game was young, before the cross-realm nonsense (which started as a pvp\battle ground thing and from what i understand now escalated to the actual world\pve) if you saw someone, and then took an action against them, that someone had a name, a name worth (maybe) remembering, for you would bound to meet again, and next time odds might not be in your favor, same works for helping out a "foe" with some mob\quest
It was a community, you had foes, you had friends, there were inside jokes, it was awesome.
but when you introduce cross realm - you simply render it all impersonal, once battlegrounds became cross realm the first thing that happen was that everyone were happy, no more horrible wait time for games, oh joy, yeah but... you never again saw foes that you cared for, everyone you meet in battle became just there class and gear (and don't, be it gear score or their actual gear from what you can tell of it in a glance) it became just an "do your automated rotation vs that X combo" and not "oh my god its anise, run for your life" (anise being a nickname of some feared warrior, for example)
Same go for outdoor activity:
at first it was good, you could be questing or going to a dungeon and oh boy you meet an enemy guild on the way, then there were flying mounts so you never actually bump to anything which is super bad, with same effect:
At first everyone were like "wow this is so great i can get to places so fast" but then they realized "I'll never truly have to decide if to fight\flee\hope not to be seeing" (at least not in the same way they used to)
And once you add portals to places (sense with each exp the world grew bigger.. some shortcuts where necessary as otherwise it would take over an hour to reach places) things simply went impersonal
and then just to put a final nail in the coffin they added an automated cross realm activity group matchup system (LFR [looking for raid]) similar in nature to non team-based battle grounds (pvp) this one was for dungeon it would simply dump bunch of strangers in a a dugong, instant queue at times (miles and beyond better than having to setup a guild [build community] select people [make friends] defeat boss together after months of attempts [enjoy the true game])
the entire nature of the game changed, sure you could walk by foot and create a guild of foot walkers but the fasters ways are easier and more convenient, getting gear no longer means what it used to and its now all about the numbers (like zero punctuation says..) and sense every major patch and every exp resets everything... the wind gets blown away of your sailed pretty quickly.. and then it hits you that you no longer have friends to fall back to
you see, it wasn't a problem at first (for some) as they already had working guild\community, sure it became isolated community but they could stick to it and have their fun with their mates, but once that guild broke up due to sufficient number of people leaving after couple of years (be it 4, 7 or 9) they had nowhere else to go, there are still guilds, but it's really not the same.
Out with the old and in with the new
this makes room for the newcomers, iirc at some point blizzard said that in total there's 45milion players, with only 12milion ever being with active account status at the same time, so many left, many came, and what do the new people know? What they see, and what do they like? What they got in for, so what blizzard does? Make more of that, who don't care for this new stuff? The old people
Are they still even relevant? Think, all the 18 year olds are now 27, they might even have kids now, new jobs, out of school.. The 30'ish that started in the games lunch can be 39 now, much can change
so wow might no longer be the thing that fitted my generation and that worked for me so well, but this not necessarily means it's the end of wow, the system still works, several million monthly players proves so, it just build for different people now
And I'm not even sure if the likes of me are relevant any more
Stop trying to burry wow; it's not going anywhere, not for a long while