Well, she had a different costume in Deadly Alliance, so that's something, but her costume in Shaolin Monks is actually a bit different. When you think about it, though, few of the main characters in the series really ever get drastic changes to their costumes. Even looking at Scorpion and Sub-Zero now, they'll make little updates here and there, but they're still basically wearing the same costumes that they did in the first game, you know?
I feel your anger, though. Kitana's been my favorite (after Scorpion) since MK2 came out, and for some reason now the team just gets really lazy whenever they stick her in another game. I'd like it if they could, at the very least, make her a powerful character again. Back in MK2, she was one of the most powerful characters in the game, but now they're content on making her one of the weakest in the game.