Variety, the game seeks variety. I often find with sequels they adopt a lot of the previous game mechanics while not employing anything inheritently new or different about the game, causing a franchise to become tiresome and dreary. We know what to expect and the character become wooden and untangiable. Ubisoft were trying to learn from their mistake of making AC too repetitive and I think even though the points raised had merits, the comparison to Shadow of the Colossus was unecessary and rarely applicible. You can only really compare a franchise with another. While simplicity keeps a game fresh, I find it to be a one trick pony often causing disinterest if continued for an elonged period of time IE a game franchise. And because SotC was a standalone game with the only future for it was a film adaptation, it's neigh on impossible to make a comprehensive comparison.

With Assassin's Creed I believe that if they didn't include "everything but the kitchin sink" the franchise wouldn't have become as large as it is today and even though it can be opposed, perhaps all games, no matter the genre, need that hint of the RPG flavour.