Although the D was good last year, the real question is: can it be better? Unelected lifelong politicians are cool with something in the organization being good. Winners, and those looking to be elite, are not satisfied with good. If Manny doesn't want to make any defensive changes, then OK, but it better get back into the top 10 or he (assuming Manny hasn't been fired for the 2021 season) needs to make changes.
Right off the top, I can tell you that the DL doesn't play with the same amount of skill, moves, and efficiency as it did with the 2 previous DL coaches.
If these donors are serious about getting us back to elite, then Manny should give serious consideration to hiring Simpson away from the NFL and bring him back to direct our D. IN fact, if Simpson has aspirations of becoming a DC, I'd give him a co-DC title, get rid of Blake and have Manny run the D and call the plays with Simpson. Getting side tracked here...
Anyhoo, good should not be good enough. All positions should be looked at and if we can do better, then we need to make a change and right away on the D side of the ball.