It’s hard to articulate, but … part of the reason I settled into playing Horde originally was because I liked the idea of playing out a redemption arc. The dark past was mostly behind the Horde when I started in BC, and while there were bound to be individuals who messed up (or had different agendas), the faction as a whole was supposed to be proving its value to a world that hated it for its past mistakes.
I didn’t want to have to play through the mistakes and horrors that the playable races will never forgive us for. And Thrall can’t make them go away. Arguably, he indirectly caused some of them by appointing Garrosh–I think his degree of responsibility for Garrosh’s crimes is often overstated, but he doesn’t stand apart from the things that have happened in the playable game, the way he does from the crimes of Old Horde.
The faction fantasy I wanted (and in fact, was promised) just isn’t possible anymore, and Thrall can’t fix that.