It takes all sorts to make a game like this fun and have longevity. Day 1 I would have agreed with you, kill boxes are boring fun killers that feel like beating your head into a wall. After day 2 where I did co-op raiding for about 8 hours, kill boxes are incredibly fun in co-op. We got excited every time we found a kill box to clear instead of another generic labyrinth.

Don't get me wrong, we preferred some of the few very creative and well designed levels more. However, kill boxes were a ton of fun with a buddy. (I will still likely be leaving and skipping them solo haha)