People have a fundamental misunderstanding of how NFL defenses adapted to what seemed like the inevitability of half the games each week featuring two teams scoring more than forty points each. Remember that Chiefs vs Rams game on Monday Night Football in 2018 and how everyone said THAT was the future? The Chiefs have scored more than forty points in a game only twice since. The Rams havent scored over forty at all since.
This happened because defensive coordinators realized that in order to beat these offenses that look to score quick the best strategy (by far) was to take away the big play and force opponents to put together fifteen-ish play scoring drives if they wanted to get in the endzone. That's a lot of plays to go without somebody on offense making catastrophic mistake resulting in a turnover or a holding penalty creating a 1st & 20 or 2nd & 20 situation (basically a death sentence for a touchdown drive).
By and large this has worked, but it will give the illusion that a defense is playing poorly because they give up more than a dozen first downs in just one half of football. Or that the sack numbers aren't where you'd expect them to be.
That said Mack has underperformed since his relatively impressive start and Quinn basically disappeared the same time the Bears loss-streak developed.