I don't think it depends on age, most of the game is pretty simple and I think it's rated 3+ so it's kid-friendly enough. Lots of people of different ages like it so my guess is that it's just a matter of what people find fun. I actually used to think AC was pretty boring and if I'd been given the game at that age I wouldn't have bothered either. Same reason why some kids like calmer toys and real life games, while other kids like more fast-paced stuff.
(I'm not just replying to you but also to the person who asked about his age... my point being that I don't think it depends on age so much.)