Assassin's Creed Rogue is very similar to Black Flag; this featured the same combat and general gameplay ideas that the series always had, but must navigate the seas on a ship. This time you play as Shay Cormac who begins the story as an Assassin but soon switches sides when he sees the destruction of the artefact that the Assassins desire.
The story could be really dramatic since Shay has to turn against his former friends, but I think it is delivered in an underwhelming way. It doesn't make a massive change to the gameplay either, since Shay still behaves like an Assassin.
There are a few new ideas, but these are delivered in a basic way. A new enemy type called 'Stalkers' is introduced who are Assassin's that hide in hay bails, grass, or rooftops. They will then take you by surprise if you aren't careful. Shay is skilled at detecting them, so is alerted to their presence by some freaky whispers, and can detect their general direction when activating his "Eagle Vision" ability.
Sometimes there will be "Frontier Battles" where you must quickly assist your allies in their war. It can be quite frantic because you will be outnumbered and must prioritise protecting your allied soldiers.
In previous games, there was a mission type where you take out an Assassin Contract. Since you are now a Templar, the mission is reversed and you must protect a target. You must scout the area and kill the Assassins in the time limit. This seemed poorly implemented to me, since the Assassin's just stood around, waiting for you to kill them unchallenged.
There's a grenade launcher that can launch sleep, berserk, or shrapnel grenades which have a small area of effect. You still have the blow dart for sleep and berserk effects, but the grenades are great when guards are clustered together in conversation.
Naval combat feels exactly the same as Black Flag, but you can now be boarded. If you defend successfully, then you get the same rewards as if you boarded their ship.
There's not as much swimming as there was in Black Flag. Some areas have freezing water so you have limited time before your health depletes. The underwater sections where you avoided sharks whilst searching for treasure have been removed.
Abstergo missions are similar to Black Flag. You play as a silent character from a first person view. You hack into terminals then return to your computer Animus. There's barely any substance to these sections so I don't understand why they even bothered with them.
I felt I didn't care about the characters as much as Black Flag, and I also felt the boss battles were underwhelming. Too often, you could take them down with basic tactics such as using a smoke grenade then killing them in one attack. The final mission is also very short and nowhere near as grandiose as an ending should be.
Despite the tweaks to the game, it plays a bit too similarly to Black Flag, and essentially feels the same game as any other Assassin's Creed. They really needed to put more emphasis on the new ideas rather than the casual approach they went with.