It's a team game, and the coaches are part of the overall effort. I think it's obvious that the coaches have proven their ability to teach proper technique and scheme over the years, so when there is a sudden dropoff in execution I put that largely on the players, absolutely. And guys who know far more about what is going on than you or I (Blaine Fowler, Dave Nixon, Brian Kehl, Jonny Harline, etc) seem to support my conclusion that it isn't the play calling or scheme as much as it is the on-field execution.
So, should the coaches go with a scheme that is easier for all the young guys on defense to execute? That's a two-edged sword if you ask me, because maybe it leads to better execution, but an easier scheme could make it easier for the offense to execute against. I don't know the answer to that one. I do think it's a mistake to want to toss away men who have proven they can do over many years for a 4 game stretch that has obviously been very bad.