FC: Primal isn't a bad game; it builds off the solid foundation of combat from the Far Cry series. The issue, however, is that it feels kind of like a lesser version of its sister-games. In general, FC3 stands as probably the most innovative and best of the bunch, whereas the following games are all kind of a copy of it, but in an inferior form in some way. FC4 was still great, however, because of the unique setting and addition of a few interesting gimmicks and weapons (such as the grapple). FC3, however, still had the better story and ambiance. Still, FC4 was fun to play, and the gameplay itself was definitely not a step backwards.
FC: Primal's main issue is that it -does- feel like a step back. We already knew that they were going to take away our guns, but when you replace them with a lackluster arsenal, it just feels like FC: Primal becomes some sort of a DLC for FC4. The game is fine, and the ambiance is nice, but overall, one can't help but feel like it's essentially a FC-clone with guns removed. Spears and clubs are functional, but with the removal of certain freedoms of mobility, a multiple array of weapons, and explosives and grenades, it just feels kind of gimped.
Overall, the game should be commended for doing as much as it does without FC's usually array of fantastic firearms. The game is fine, but it's likely not going to be something you'll remember for very long, despite some authentically enjoyable and funny moments.