I think that WoW is no longer a MMORPG since years, I'd dare say from WotLK onwards it slowly but steadily changed and became the lobby game that it is nowadays and lobby games need difficulty levels. I believe that TBC, while shitty on the dungeon design, still was an MMORPG, with the RPG part starting to fade.
The open world is completely useless and certainly underused, people can quest in a zone and skip more than half of it because quests become grey, this at a normal pace, if you have a full heirloom set, it gets ridicolous, if you add the level appropriate dungeons, you basically don't even know what happens in a zone anymore.
There is nothing even remotely threatening anymore: you can go afk with a mob pounding on you and come back 5 minutes later being still alive (2 mobs can still kill you, after a while), but more than that you can probably pull as many mobs as you can (before they leash) and AE them down without problems.
Dungeons are soloable with heirlooms, never tried without, but certain classes may pull it off probably. This is because low level people must be completely and utterly retarded and they play with a thumb up their asses all the fucking time I guess. Soloable dungeons. Think about that.
WoW lost the magic, it's maybe worth to pick it up for a month when a new xpack releases, but to be honest, any other RPG on the market is a lot more appealing now, the other players may as well not exist for how good, useful and fun they are, may as well play with controllable NPCs. A few friends of mine still pick it up now and then, but it's their OCD personality that pushes them to get achievements (lol) or "finish" a content patch (aka clear the LFR raid).
There is (was?) a lot of good stuff in WoW, but the game changed over time and apparently a lot of people don't like the changes much. You can say it's because of its age, but I wouldn't believe it. People nowadays speak with their wallets, not so much on the forums: 3 millions subs lost in a few months testify to that.
Would I go back playing vanilla? Well, I did in a 1.12 emulator and I must admit some things are outdated, especially in the downtime department, but it still feels like a world and I still have that good old slow progression feeling, with a mini-exciting moment when I get a new blue weapon that makes me feel powerful for a good while. I would probably play a game like the old WoW again, maybe not exactly the same one, I have 11 level 100 all raised manually xpack after xpack, there is no space on any map whatsoever I didn't see at least once, including hidden and unaccessable areas where it was possible to exploit and enter anyway.
Modern WoW can keep me hooked for 2 weeks top after a content patch (not 6.1, I still laugh about that "patch"), so it's hardly worth to pay a month for it. I'm eager to see all Legion features in detail.
