The Jets were using Vilma correctly and decided to go in another direction. That's one thing. The Giants were using Saquon Barkly correctly and decided to go in another direction because they didn't value the position. The Buffalo Bills did not re-sign cornerback Jabari Greer largely due to financial reasons and chasing high-profile free agents like Terrell Owens. The were using him right though.
These were all huge mistakes made by each respective team's management. Front office strategic errors are one thing. Talent evaluation errors are a completely different and not mistakes you want your defensive minded head coach to make. Allen is a genius when it comes to the secondary, but the errors in the front 7 are hard to overlook.