I don't like Claymore, I don't like Wraith, I don't like ship combat, I don't like Polar Bears, I don't like..... GRAAAAAAH!
I do like polar bears. We penguins use them as war horses. We ride them into battle.

Well if you don't enjoy the sailing part I can understand how boring it can get. I personnaly thought I wouldn't like it, was very reluctant but in the end I really loved it and I still can't believe the amount of time I spent at sea singing pirate's songs, making this my favorite Assassin's Creed yet.
Amongst the many complaints I have about this franchise, one of the major is the way they end the games. I'm not sure why but no matter how much I enjoy the journey, I always get extremely disappointed and frustrated by the last couple of hours of gameplay. There's not a single ending I liked. It's not like I get uspet because I don't want it to stop, I just don't like them. Am I alone in this case ? Am I cursed ?
That was what I first did with my first EVER playthrough on ME3. I stopped before the Cerberus base. That was before I knew how everyone was complaining about the ending, or that it was even one of the final missions. I still have that save game on my PS3. Why? Because no matter how many times I finish the trilogy in my other playthroughs, the story will have never stopped.

I didn't want it to end. When I was younger, it was rare I actually completed a game for that very reason.

Anyway, back to your point about not liking the endings - Assassin's Creed Syndicate actually did it quite well. For most of the game, the story feels somehow disjointed, and you're not exactly sure where you are in the grand scheme of things other than hunting down Templars. But the final mission is awesome. One of the best levels from any game imo. I have a list.
The best video game level that I've ever played is, for me, basically everything that happens during and after the Hotel in Batman Arkham Origins. I just love it, I have no idea why.
Second best is the Suicide Mission from ME2.
Third is the final mission in ME1.
Fourth is the last part of Batman Arkham Knight when you're looking through the Jokers eyes... it's just awesome.
So... I'd reckon the ending of AC Syndicate is about 10th on my list?