So I'm finally playing this. Think I'm about 1/3 of the way in. It has some great aspects and some not so great.
Really enjoy the duals and I like a lot of the side quests, both the single ones and the multiple mission ones. The shrines and haiku and fox dens things can be frustratingly time consuming and repetitive. The characterisation is pretty weak at least up until this point. Certainly when compared to the likes of Red Dead 2, The Witcher III, The Last of Us 2. Although it's better than AC: Odyssey. Probably on par with AC: Origins for that aspect.
Graphically it's a bit odd. On the one hand you have fantastic looking areas like the golden forest particularly at sunrise and sunset then you have some of the worst looking water effects I've seen in this console generation, especially at the coast. The water and waves are laughably bad.
Multiplayer has been pretty addictive. It's grinding for better gear and loot but I just enjoy this game so it doesn't feel like a chore. The story mode co-op missions are neat, I like the narration and style that they chose to go with. I haven't done a raid or anything yet but I am really enjoying it.
It's funny, when I beat the single player campaign months ago, I loved all the customizable items you can find but I kept thinking "man, what this game is missing are some cool Oni masks" and sure enough, the Assassin class masks are largely oni masks.