Good defense- in any sport- starts with being strong up the middle. At NT and ILB, the Packers just aren't very good. Not much in the way of talent, speed, or physical play. Since there's not gonna be an extra draft or free agency period before next year, that's unlikely to improve much, if any, this season.
They'll have to rely heavily on good schemes and calls.
I agree that good defense starts on the LOS, and being strong up the middle - unfortunately, TT/MM/Capers disagree. Everyone and their mother can see that we're dead at ILB; yet, Brad Jones and AJ Hawk are still our starters.
MM said he was going to get involved with the defense to ensure that the problems were addressed and fixed - and what we got was smaller and weaker along the DL, and a base defense that went from a weak front 2-4, to a weak front 2-5...
MM did not have to go along with Capers gameplan that called for only 4 active DL in the opener, but of course he did - and then when we got predictably gashed in the run game, we got the same old tired speech about "... we'll get that cleaned up".
Eventually a rational person has to conclude that the Packer philosophy on defense is all about finesse; that the NFL is a passing league - and only a passing league, e.g. planning to stop the run and control the LOS are not really necessary; etc.
Combine those realities with TT's perpetual youth movement, Capers complicated and unsound coverage schemes, and you have a recipe for disaster. The players are not good, the coaching is terrible... there's no fixing this mess - and nothing will be done about it.
The Packers braintrust believes that stopping the run is incidental, and therefore need not be accounted for in acquiring personnel or formulating gameplans - they believe that every play is going to be a pass, so they design their defense to stop the pass - and only the pass. Unfortunately - they don't even do that well.