melee is the main culprit, but ranged is pretty bad as well, though not as bad. the zombie ranged attackers can see you behind hatches and barf at you from the back of their heads while facing the opposite direction with 360 no-scope accuracy from maximum range. when bandits armed with firearms are introduced, it's probably going to get worse. and it will never be at the same level of quality as a dedicated FPS.
melee is just bland... step in swing, step out. run in swing hard, run out. no dodges, no blocks, no counters, no slides, no grapples etc. and even though this is less of a problem than it used to be, you do still get multiple zombie bodies squeezed into a space that should only fit 1.
and i get it, that kind of combat is not the focus of this game and that's why i mentioned that it will always be crap and if that's an important factor for you, then you shouldn't buy this game.