I'll try to make this accessible to non-WoW players :) Aside from the time thing, which is a large factor (the amount of time spent on this game was killing me), I cite three main factors, all of which stem from Blizzard's attempt to make WoW "more accessible" to anyone who wanted to play. I've grown to hate the phrase "more accessible" as it applies to gaming, because it generally means a game that's not designed to have any challenge. So how has Blizzard made wow "more accessible?"
1. Give everyone gear. In the first iteration of WoW, by and large you could only get the most powerful gear by doing the 40 person raids. In other words, it was really hard to get. Something like 4-5% of WoW players ever saw any of the end-game dungeons, so this super gear was very rare to see. In its current state, you can get damn good gear without even setting foot in a raid. One way this was accomplished was by giving the players tokens for completing the mundane dungeons in WoW. Of course, high end players did this too to get more gear faster, which made getting gear very grindy. Now you didn't HAVE to do this, but if you wanted gear fast, you did it. So you're forced to do bland, old content to get gear as fast as possible.
2. Badly tune the difficulty levels. In the original WoW and the first expansion, you had one difficulty setting. Most average players weren't even able to even see the earilest bosses in the mid-level dungeons. In order to get more people raiding, Blizzard introduced Normal and Hard modes. In its current form, 90% of players have beaten the easiest raid boss of the final dungeon in the game. This suggests how easy it is. The problem is Hard modes aren't currently released right away when a new dungeon comes out, so you're forced to play through "easy mode" for a few months. We were basically killing new bosses the first or second try, and that wasn't fun for me. Add to that there's nothing to do until the harder modes come out, so you're doing that for months. Of course, this isn't fun for the highest end guilds that compete for world firsts, so when hardmodes came out, they were RIDICULOUSLY overtuned so that the top 100 guilds in the world would have trouble killing them
For a guild like mine that's pretty hardcore but not world class (we were around the 95th percentile worldwide), that's just impossible to beat. So we were faced with killing EZmode, which was boring as fuck, then we'd do the hard version (in some cases they were actually two separate dungeons) and spend three hours a night getting the shit beaten out of us for a few weeks. This soon became apparent, and blizzard started losing players, so they introduced a monthly (or so) 5% stacking buff to HP, healing and damage done, which allows guilds to gradually work their way through hard modes. This is pretty stupid too, because essentially you're just waiting around for the game to make you strong enough to beat certain bosses.
3. Dumb down the game. When I first started raiding, I found it exciting and challenging to be the best player I could by mastering my character. As WoW progressed, this changed. Without getting too WoW-technical, certain things you had to do became automatic. As the game grew, players got more abilities that trivialized certain duties, and the gear became more homoginized. The latter point was a big issue for me. I used to enjoy tailoring special sets of gear for different bosses based on the type of challenge the boss presented. Kinda like in Vagrant Story where you could re-gem gear or make new weapons to handle specific enemy attributes. Now the gear is all "one size fits all" for most bosses. To make a ridiculous, exaggerated analogy, let's say that when Pac Man was released, you had to do the following basic things:
-Eat the dots
-Avoid the monsters
-Manage power pellets so you didn't run out of this resource too early
But after a few years, the developers thought this was too much for your average person, so they made Pac Man invincible. How much fun would it be if all you had to do in Pac Man was eat all the dots?? It's the same thing with my WoW character. All I am now is just a damage sponge. It's boring.
There are a ton of smaller things as well, but I don't think they'd be interesting to a non WoW player as they're rather WoW specific.