It's actually a function of the overall defense and not a problem at all. A 'simple' defensive line scheme allows our LBs to read assignments quickly re:gap vs rush and keeps underneath clean on pass downs.
The defense is only DB-centric because we picked up Hyde/Poyer. There's more talent right now in the secondary, which is why McDermott leans on it more than the other units. But he's always going to find pieces that work and plug them in and adjust accordingly. It's not as if his defenses were always predicated on a strong secondary...he got NFL starter-level play out of Tre Boston and Bene Benwickerie for christsake. Historically, McD has needed 3 things to run a top defense- a Pro Bowl level corner, a crazy athletic MLB, and a 1tech DT willing to play gap control. The rest he can adjust scheme to fit pieces.