Well, in fairness to that crowd, Rex has hired his first moderately competent OC in, well, 6 years. And he has produced some darn good defenses throughout most of his career.
Rex will get the defense straightened out, IMO. The only problem (and it is a huge problem) is that Rex will get the D fixed by making personnel changes. The loss of our Pro-Bowl caliber 4-3 personnel will happen. Will we ever seen a defense the caliber of the 2014 season? I doubt it. But we will be decent to good again. Good enough to maintain a playoff and Superbowl window? That remains to be seen. The modern NFL doesn't allow for those windows to last long, no matter how good of a HC/DC we have. Our playmakers will age, or get figured out. We will lose FAs. Players that would be improvements to the team will be lost to FA. I see us backing into a playoff spot in the next 2 years, getting bounced, then suffering a couple 7-9/8-8/6-10 seasons, then another regime change in our future. Maybe that's progress. Maybe not.
A step forward, 2 back, and then some side-stepping. A hallowed Bills tradition.
Yes it will be better. Because we'll get rid of the players that don't fit, and hopefully find a few that do. We won't draft/sign 2 Pro-Bowlers.
And maybe I have higher expectations, but a drop from #3 to #20 is unacceptable. Point blank.