I hear you re: secondary play improving and the ability to play less conservatively, less vanilla if you will.
At the same time wht we do with the secondary will be domino 2 as plays develop. Domino 1 will be whether we have a pass rush tht can get home, disrupt QB timing, force hurried or offt-target throws. If so, corners can cover aggressively from LOS for, say, 2 seconds (depending on alot of variables) in man-zone after the snap and break up or intercept a lot of passes. If the CB's are losing the WR's after, say, 3 seconds because there is no effective rush, you're risking completions where the WR has separation from the CB. Let's say this happens at the seam of a zone and the safety is arriving late... you get the idea.
My point: A viable rush opens things up for the secondary - moreso than improving the secondary at one position.
The ability to contain a passing offense w/o getting burned when there isn't much of a rush leans toward conservative deep CB play to contain the big play.
If you have a rush, the QB and OC on the other side lose a lot of wiggle room, as the CB's have time on their side to play tighter coverage. Instead of completions where the CB gets beat for big yards after a WR finally gets open, you're looking at broken plays, or a CB jumping a hurried throw and taking it ot the house.