Crysis was taxing because of the lush flora. All we have is speculation why AC runs so terribly. PC has worse textures than the xb1 and the game is "optimized" for the gtx 680 but still manages to get shit framerates on higher end hardware.
How is ubisoft pushing the envelope/hardware? What purpose does your white knighting of ubisoft do? Why dont you direct your questions at them? You're not the only one who can ask questions.