This is a fallacy
The Bills should be using average CBs because that is what the scheme they use is designed for. They would not be giving up long TDs because of the cover-2 safeties playing 30 yards off the ball, to back up the CBs playing 10 yards off the ball.
Since they are so committed to the soft cover-2, it is absolutely stupid and counter-productive to keep using premium picks on CBs with elite skills only to waste them in soft zone coverage.
If they built the OL and front 7, they would be able to control the line of scrimmage