Your issue is that you're only aiming for the head. Like it's supposed to feel awful to fight. Because survival is the goal. It's like trying to play MGSV like a traditional cover shooter.
Killing zombies is part of survival because it lets me create safe areas that I need to traverse frequently, lol. Like I know it's possible to dodge 100% (or maybe 99.99%) of all enemies if you're good enough, that's not an average play experience. The same tension of "should I leave this zombie or should I clear it" will still exist if they don't take so many headshots to permanently down anymore (sans crit or power ammo), because being less generous with ammo compensates for them being easier to kill. You'll still be forced to think carefully and aim well.
If you're just telling me I should be kneecapping everyone then not finishing them, that may be more optimal since they are easier to dodge but it's also extremely silly.