pretty much this, this isn't a hard thing to understand.
video games as a developing system are iterative and duplicative, you don't need to redesign the wheel you just need to make sure the care is fun to drive.
yeah, it took alot of elements from other franchises that in turn took from their predecessors, get over it.
it's a fun game from what i've seen of it in play, i'd definitely suggest you at least research it since it's by and far better then other post-apoc zombie shooters with how the zombies aren't jokes you'd have to be stupid and blind to die to.
the way they flow over the terrain and each other simply puts too many bodies in front of too few bullets, further distict that with a variety of elite zombie alternates and even zombified animals along with an AI that actually gives the zombies a truly voracious nature(they'll eat the corpses of dead zombies even killing weakened ones if there are no bodies nearby).
in short, it's about people fighting zombies, not bandits, not wastelanders, not randumb evil why faction #476, just an endless teeming horde of the infected walking dead looking for any kind of meat to eat.