You didnt play with shotguns enough in KF1 then. Shotguns also lose the penetration if you stand too close. So in KF1 you need to me 2-3 meters away from your target to get the full damage in. But at that range some pellets can deal damage to both hitboxes of the zed, so you do more than normal damage.
As in KF2 with you are fighting gorefasts/crawlers it gets most noticeable. If they use the jump attack to get in your face, you cant hit them. I may miss the head, but no way in hell I am missing the body which take over 70% of the screen. And if the crawler is right at your feet, you need to take a step back or crouch to hit it.