The head coach is responsible for hiring & firing his staff. Harbs has, in his time in Baltimore, surrounded himself with very experienced coordinators and one of the largest (and presumably most expensive) staffs in the NFL. Harbs is a great head coach in nearly every area, but game-day decision making and selecting coordinators (especially on offense) isn't his strong suit. On defense, the inability to hold a lead is a hallmark of the Pees defense, regardless of players. Can't be any excuses for the D after this draft, that's for sure.
On offense, we have migrated from a power running, deep pass attack of Cam to the zone-blocking, play-action pass style of Kubiak to whatever the hell Trestman and then Marty tried to Frankenstein together. Firing OCs in mid-season has become a disturbing trend. Not sure what the identity of the offense will be now, but it seems as though the talent is lacking in many areas to execute much of anything very well.
It all circles back to Harbs. His coordinators and his staff are a reflection on him, and he doesn't have any room to make yet another major shift.