If the players keep doing things that the coach is telling them not to do, or numerous players consistently under perform, yes that is on the coach.
You can always use the excuse that the players don't execute. Maybe it's possible Maclean was a good coach and the players simply failed to execute his system? Doesn't matter because at the end of the day it's the coaches responsibility to make sure he has a system that works AND that it gets executed properly on the ice. And if one of those two things aren't working, or if many players on your team are all displaying the same weakness (in our case offense and an inability to hold a lead) then it's the coaches job to figure out how to fix it (whether that's through a system tweak, or one on one teaching, strategy adjustments, etc.).
Seriously this is not a team full of AHL scrubs. Perhaps there's not a whole lot of offensive star quality, but our D shouldn't have issues keeping a 2 goal lead on a consistent basis. How can that not be on the coach?