I think its biggest issue is the scale of things. Ubisoft wanted the world to be the entirety of Greece, but to pull that off they made everything feel tiny. It's especially noticeable when you're at sea and islands are at most 1-2 minutes away from each other. I think some other AC games (III Liberation) are worse, but it's definitely my least favorite of the RPGs.

@ShenronKagura One of the problems of Ubisoft today is their focus on quantity and not quality. They should try to make smaller but memorable experiences instead of making bloated abominations just to be able to say that they've got hundreds of hours of content. "Short life and a merry one" as Bart Roberts used to say in Black Flag.