I liked several aspects of the game - Haytham is a great protagonist, and the setting is unique for video games. However, Connor and his story are just so DULL. He only gets to display emotion and express a damn personality a handful of times throughout the story; everywhere else, he's just being ordered around or reacting flatly, and the rest of the characters don't fare much better.
The cutscenes are also dull. Characters remain in one spot at all times, mannequins delivering their monologues with little to no human expression, and the background audio remains dead silent.
The cherry on top is the ending, where you have a worldwide apocalyptic event you've been building toward for five full-length AAA games; how do they stop it? Desmond puts his hand on an orb and dies.
How does it work? What exactly is happening to stop massive solar flares from cooking the earth? Because the game decided that THIS method, the most important of them all, wasn't worth explaining beyond "it will work."
It felt like an insult to everyone who invested their time, money, and energy into the previous four games and built up their expectations for what the saga's conclusion would play out.