Thats not a change in systems. That is quite clearly players unable to execute the system.
The argument that AV is too stubborn with/too married to his gameplan is a legitimate one. What you are doing is taking diminishing returns due to a diminishing roster and blaming that squarely on the coach. Its a crock of an argument.
It's absolutely a change in systems. Anyone who can play this game at the NHL level (hell, almost any level) can do those things.
Again, those things started to change in 2015 when he had arguably his most talented roster. The man to man is what it is, but its only a huge problem because of the way that this team plays in the other 2 zones - one and done scoring chances (at best) in the offensive zone, unimpeded entries for the opponent into their end and then near countless high end offensive opportunities. The system sucks, it sucked even when they were ultra talented.