Does it really nullify the criticisms of sexism? The Self Actualization arc remains mostly the same, Hermione is one of the characters that gets the least "upgrades" compared to canon for most of the story, so is McGonagall she's still fridged for the sake of Harry's quest (although I don't think that fridging is a good criticism), she ends up awesome through no actions of her own and her future is steered by Harry. People who criticized HPMOR for being sexist won't change their mind because of this ending.