For Assassin's Creed, it was so repetitive even within the same game (the first one) I couldn't even finish it once I noticed the grind. It drove me nuts.
A lot of games then followed that pattern (e.g. Shadow of Mordor, Mad Max, and I'm sure countless others -- I just mention the ones I tried). I find some of their mechanics interesting but once the grind kicks in (which is fairly soon, since these sandbox games are all grind-based) I despair and abandon them.
They feel like repetitive work rather than entertaining to me.
But hear this: Papers, Please, a game that is literally a bureaucracy simulator, engages me in a way Assassin's Creed never could. I wonder why! (Random guess: I think it's because PP, for all its repetitiveness, feels like a small game, while Assassin's Creed and its like feel like endless games you could spend your life within... and I have better things to do with my life).