For the record, I'd be open to replacing DeBoer. Whatever it is, he's been the coach for four seasons and there is no cup. That is a good enough reason. But, I'm not sure you can fault him for the system failing.
Not only can no system survive the frequency of mistakes, poor goaltending, and lazy attitudes, but currently, the players aren't holding up their end of the bargain in terms of their hard skills. This is now a team that is built off its defense, and Burns, Karlsson, Vlasic, Heed, and Prout all need to step it up. The mobility, zone-entry, and passing ability this defense is supposed to have has not materialized.