What I've picked up:
1. Hubris (I've heard from several ex-Blizzard coworkers that senior staff has absolute power)
2. Inability to adapt to modern principles of game development (for example, my friend said that they rely primarily on intuition and not on established best practices)
3. They're making too much money (same problem with Riot; there's too much money coming in so they're bad at holding people accountable)
Caveat here; I also have friends who work there and love it. If I had to guess, I'd say their problematic departments are (1) production, (2) dev management, (3) finance/top leadership, and (4) game design.