I enjoyed this game a lot, so if this post sounds negative - I don't think the game as such is bad at all, but there were various things I did not enjoy, and I actually skipped quite a lot of content, which is a downgrade for me after Odyssey where I did everything.
Anomalies - gave up on them
Tattoo Papers - Didn't bother with most
Cairns - gave up on them, though much later than the anomalies
Drinking game - sucked at it, felt no desire to get better
Norway - too much time spent here before going to England if you try to do everything
Pacing - too hard at the beginning, too easy at the end
Lots of stuff in the world gets repetitive, including curses, mushrooms and last but not least loot, where the effort to get at it often doesn't feel like it was worth it.
Best gear comes so late in the game it feels pointless.
Opal farming - very repetitive quests.
Zealots - not being able to use assassin tactics on them - at least it didn't work for me. In general, I'm not keen on being forced into tons of 1:1 fights in an assassin game. Mercs in Odyssey were a lot better.
Good: Story was overall great in the game imo, same for the characters.
Settlement - in general decent though it could have been better (I felt no desire or inclination to do the hunting or fishing content, both bc I don't enjoy slaughtering non aggressive critters in games and bc it just felt inanely grindy). It felt a lot more part of the game than similar elements in, for e.g., Black Flag.
Skill tree and some of its features, especially missile reversal.