Without veering too much from the essence of the series, I found it different enough to make it a refreshing spin on the Far Cry formula. The gameplay makes honor to the title, feeling more primal due to the focus on rudimentary weapons and the importance of the gathering and hunting... and the combat doesn't suffer as much as I feared with the change. I was afraid that the lack of modern guns would make things less interesting but, while the melee weapons feel a bit too basic and there aren't that many, throwing spears to impale your enemies and trying to master the bow and arrows to be able to silently clear an outpost never got old for me.
The open world could be more varied but is beautiful and fun to explore, full of animals that look great and have realistic behaviors that add a lot of life to the scenery (you quickly, maybe too quickly, get powerful enough to not feel too threatened by most predators, but the first time I watched a pack of wolves hunting at night, their glowing eyes suddenly looking at me, was an amazing moment emphasized by my vulnerability at that point). The story, characters and the companion beasts you can tame were more engaging than I was expecting, the plot is simple but made me care more about helping build the small village in the game than some games about their big "save the world" stories. That said, the side missions can get repetitive, although I enjoyed them for a good chunk of hours while I collected all the materials and skill points needed to get the available upgrades, and the story missions have some highlights but, in general, are not too memorable.
More info: https://en.wikipedia.org/wiki/Far_Cry_Primal