Wrath of the Lich King was the most successful expansion in WoW history. It peaked at 12.3 million subscribers, it also had a fair amount of accessibility, significantly more than The Burning Crusade. You cannot argue with results and most people look at Burning Crusade as one of the best expansions but thats because they look with 'rose tinted glasses'. They don't take into account the massive rep grinds, the inaccessibility of content in general (not just raids), and absolutely terrible class balance. Class balance is in a way, indirectly linked to accessibility. I played a Shadow Priest when they had awful numbers, you were pretty much just there to be a mana battery and thats it. If a group already had a Shadow priest that was decent, I couldn't get in the raid or guild because why would they want a class with terrible dps. The point I'm getting at, was this directly affected accessibility for not just me but all shadow priests.
The same is true for League of Legends. Not everything has to be easy, but things should be accessible. Champions, specifically should be accessible, yet there are some that remain largely inaccessible. The fact is, it's incredibly difficult to succeed with champions like Ziggs or Wukong or Viktor at a high level because these champions are just lacking. I have a buddy who is a pretty good wukong player, now granted wukong isn't absolutely awful, but he's certainly good, not a strong pick for any role currently. He has spent a lot of time mastering wukong, but because wukong is fairly weak, his accessibility to success with wukong is diminished than say if he had spent as much time mastering a champion like Elise. I know it's not a perfect comparison, but the point is still fairly true. Game balance should be the primary focus. And your comments are very concerning because it shows the utmost contempt for game balance. The Burning Crusade was arguably one of the worst expansions as far as balance, perhaps even worse than Classic (coming from someone who has played since the first month of WoW). It also had extremely limited gameplay (not just raiding as I said), yet you seem to think that it hit the spot. Will you refute what you said? Because quite frankly your idea of a 'sweet spot' probably would have killed the game if it had continued in the direction it had.
The idea of an MMO style game is just that, a massive multiplayer online which allows for accessibility to magnitudes of content many games cannot provide. Yet you seem to despise the idea of accessibility, which makes me wonder why you're even in the MMO business