Scheme, scheme, scheme.
Every team that plays us says the same thing, "they don't do anything hard on defense."
Historically, we had the players to leverage that. Thomas, Chancellor, Sherman and company in their prime and healthy, we could afford to not develop game-specific schemes. We don't have the talent to do that now. The "just go out and play" mantra should not apply. We need to reinvigorate the scheme and get way more aggressive.
Teams know exactly how to attack our zones, as they have had years of trial and error to perfect it. Our system is built on pressure, so if we don't get it... this defense is easy to attack. You do have the QB to do it, like the last two home games we have played (Cousins and Ryan). Rodgers eats this defense alive. Wentz is going to do well against us as well. Brady would beat us sideways right now. Even a QB like Keenum would have success, he is patient and does not make mistakes and is very accurate. If we played the Vikings, I would expect to see 3 out of every 4 third downs converted and it would drive us all nuts.
We very rarely come up with wrinkles, CB blitzes, or anything out of the ordinary.
Compounding the problem, especially at home, is the crowd noise is no longer intimidating and teams easily communicate and adjust, whereas they used to struggle just to get the play off and not get a false start.
All of those factors combined are why we see offenses making plays. Accurate, patient QB + a good pass blocking line...we have no way to stop it.