This is perhaps the biggest misunderstanding of all -- and not just of the WoW community, but of many game communities in general. They think they have a voice and are being heard. At the end of the day, the game co. decides which way to steer the ship.
Consider Riot, by comparison. They know they have a game that is minimally accessible; they're fine with that. They're content knowing that their game caters to a hardcore gamer demographic and thus aren't burdened with the need to aggressively tweak the game until it is playable by everyone. To the contrary, by freeing themselves to focus on that hardcore audience, they can pursue improving the balance / functionality / features that that core audience will appreciate.
Since it's wildly inappropriate to speak negatively about a former employer (game industry or otherwise), we lack any tangible examples of a former employee going on-the-record about their misgivings. All we can do is extrapolate from various quotes and attempt to piece it together.
Example 1. Ghostcrawler, freshly hired at Riot, contrasting design choices at his new co.
1) I'm not super interested in compromising LoL design in the name of accessibility. Yes, League is obnoxiously hard to learn if you don't have a friend showing you the ropes. That sucks, but it's not worth stripping away the depth or potential for mastery for our core audience -- you guys -- in order to attract new players. That's not an approach every game can or should take, but it's the right call for League.
Extrapolation: Ghostcrawler himself increasingly felt pressure to design for a casual and a hardcore audience, knew the ramifications, and (more or less) grew dissatisfied with this approach as it applied to something he formerly worked on.
Example 2: Paul Sams (former COO of Blizzard) opining on lessons learned:
First and foremost, I learned that you must put game quality and player experience first in everything that you do. Gamers are not driven to buy games because they have a clever business model, they buy games that are fun and immersive that deliver on what was promised. I also learned that being a trend chaser or first mover is not a key to victory. Our team here at Ready At Dawn needs to make games that they love and that they want to play so that we can get the very best and most creative work out of our developers. Force feeding a development team to chase a business model or game type trend when the team doesn't love it is a likely losing proposition. A happy and motivated team that is making a game that they absolutely love with a leadership team that doesn't force them to ship their game before it is ready is part of that formula for success.
Extrapolation: Paul observed (and perhaps disagreed with) Blizzard's ongoing attempts to implement gimmicks in order to attract a wider audience, rather that dedicate those development resources to expand the depth/breath of the game for the core audience.
Without saying something that would completely damage their career in game development, you can pick up hints in these variance of opinion that paint a bigger picture about what was (is?) going on at Blizzard.
I'll expand on a lot of this stuff in one of my last blog posts, tentatively titled "Greed Before Need"