The game has really cool concept, but it also has some poor execution of those things.
-The melee combat is really bad, like actually really bad. There's no movement, parries, dodges, etc any abilities most games would have to make close up melee combat feel fair. Instead Its taking swings and kiting most of the time while doing you're best not to have random one-off bad camera angle related deaths
-AI programming is pretty bad too. The beasts tend to create more problems then be helpful when raiding camps, they get detected, or will engage enemies and cause lots of aggro for no reason.
-On that note, enemy AI is pretty crazy. When one enemy detects you, it aggros the entire camp, or somehow killing an enemy with a bow will make the enemy AI SO GOOD THAT IT KNOWS YOUR EXACT LOCATION EVEN IF YOUR HIDING. Not even Assasins Creed is like that.
-The Elite enemies are also very overpowered, and on harder difficulty they are basically impossible to fight because they can one-shot you with their swings and they are extremely tanky, It feels like even using fully upgraded weapons barely damages them.
-Lack of armor / armor upgrades makes it so I can't build or craft better armor to survive against tougher enemies or animals.
I wasn't really enjoying this on Hard mode because of all the issues the game has just makes it not fun to play. It isn't even like dark souls hard where you're rewarded for a well-timed deflect, most of the time your just aimlessly swinging at a damage sponge while trying to avoid one-shot deaths.
The last thing is, the open world map is kind of boring and bland to me. The animals are cool, but after like 50 hours in, it just starts to feel too big without much to offer.