I'd argue Hitman's AI is also pretty complex.
Is it though? I mean the AI uses the same routines in reaction to the point you are supposed to plan your routes/kills around it.
That's by design.
I think people are confused about what "good AI" means for games.
Some think a good AI is something that's as close in intelligence to a human, but actually i'd argue it's something that enriches the game's design.
This is a common argument especially in stealth games, when the "lol they're blind and so dumb" complaint gets thrown around, without realizing that a good game's AI is SUPPOSED to be dumb.
No shit a game knows you're hiding behind the box, if it doesn't see you it's because, by design, the game is letting you win.
"Real" stealth would be a miserable, unfun experience.
I see Hitman in the same way, it's a web of predictable but not obvious routines that work perfectly to maximize fun, while making the world feel alive.
Good AI is, really, the art of creating the illusion of intelligence, while maintaining a sense of fairness and progression for the player.
Nobody would want to play an FPS where the cpu can just headshot you perfectly as soon as you turn a corner.