Prince of Persia: The Sands of Time did it right. It realized that the purpose of failure in a videogame, at least much of the time, is to learn from that failure and do better next time. Part of the teaching the game is doing comes in feeling consequences for your mistakes. But it also realized that if the mistake was a single timing error after a series of perfect moves, the player should not have to achieve the same thing they already achieved, but only what they did not do well the first time. Thus, the Prince has the sands which allow you to rewind your actions to a point you were comfortable or happy with your achievement.
It is a brilliant, effective, gameplay and story appropriate mechanic.
And holy shit does Assassin's Creed need it.
Every frustrating moment in AC for me is in either repeating easy to fail missions or falling into the GTA style run from the cops, get your wanted level down loop. I find traversal in AC eternally enjoyable. I find the bad ass feeling of set pieces and the time I do stealth my way through the level perfectly intoxicating. But the game forgot what PoP fixed. And it is stupid that did.
It is stupid mechanically and fictionally. Mechanically, a probably limited rewind function, like Eagle Vision and diving assassin recruits, acts as a spell that evens the odds for the player against observant and constant guards and fast-running quarries. Fictionally, the Animus has established time-alteration abilities. It can fast forward through years. It can pause the world for a villain's soliloquy. Rewinding what is essentially false time makes sense for the Animus. It also makes sense for the purpose of the team. Desmond is supposed to relive his ancestors' lives so he can learn what the fuck they did with magical artifacts. Of course his ancestors didn't run up the wrong stupid wall and lose track of Charles Lee.
Computer rewind makes arguably far more sense than magic sand rewind.
So, my question is, why is Ubisoft so dumb and bad at making games when I am so brilliant in hindsight?