When playing with a good group, this is among my favorite games of all time: Destiny, Last of Us, Gears of War 2, Zelda Breath of the Wild, Final Fantasy VII. It requires constant communication and skill to best other players, or just maneuver the map. There is an abundance of creative ways to defeat other players. As an example, I was playing with a buddy and we were facing a 4 man crew. My buddy shot me out of a cannon, and I grabbed onto their ladder, and hid till they all exited the ship during a voyage, then three two of their treasures overboard and jumped off with another. Then I had my buddy pick me up.
The single player is tedious, since it's not easy to maneuver the ship with just one person, and it's unlikely that a single ship can overpower a team of players, so in single player it's just about killing unintelligent skeletons. The AI is just too dump, and too easy, so it's really the PVP that makes this game fun. If I were rating the single player, I'd probably give it the same rating many others are: 6. However, as a multiplayer game, I love it.