The construction of the defense is a top 5 draft pick (Hawk), a top 10 pick (Raji, though now on IR, but he was terrible last year anyway), and numerous other first round (Matthews, Perry, Jones, Clinton-Dix) and other early picks (Burnett, Hayward). In addition, free agency has been utilized numerous times to try to help improve the defense, while the offense almost never gets help through free agency. Peppers himself has been an elite player throughout his career and was the 2nd overall pick in his draft.
Rodgers, Sherrod, and Bulaga are the only former 1st round picks for our elite offense. No top 20 picks.
If the defense isn't improving, it certainly hasn't been from a lack of effort to dedicate resources to it. Either Capers is simply unable to utilize the personnel he's given effectively, or Thompson has been very poor at both drafting defense and utilizing free agency to improve the defense. You tell me.
Maybe it's poor position coaches. I really don't know. I'm not qualified to answer that question. Whatever the case may be, something just isn't working with this defensive system. We thought they were starting to turn it around last season, only for that disastrous second half of the season. They've been given a long enough leash on the coattails of the Super Bowl season. At some point, there needs to be production again.