As all the other guys, I played this for the story.
It didn't disappoint me - much.
The story practically was: 3 guys who either tried getting their honor back, vengeance, justice, seeking answers, or freedom/protecting their "people", all three of them did all they could from their early twenties to fourties-fifties, and after eliminating all threat, they had an encounter with the First Civilization telling them that they were mere pawns who have done their work so their descendant from the future could get a message but die to save the world because he ran out of time since those three guys and their respective alliances spent too much time fighting that no time was left to stop the apocalypse.
TL;DR: Their lives were just a waste, and none of them were actually remembered in the future, and being an Assassin is the job of an unemployed person who knows his way with a sword and how to climb. Optional: He should be crazy, like Connor.
And for all the achievement players, they had to go through a 17 minutes long credits to get the end achievement.
I really adored the new features, although the lack of recruiting new assassins, and you could only have 6 of them, and how did you earn them? Why, by liberating parts of New York and Boston of course! And I don't think you can customize their appearances either, although being able to give them contracts on-the-run was a good feature.
Naval warfare was a great feature, so was hunting.
I can't type more, although I seem to have a reply for every question/argument raised.
I'll try when I can.