McCourty, Chung, and Branch are all north of 30. That’s three starters who you wouldn’t expect to be as good as last year, based on normal aging and regression. I think McCourty is fine and can play at a high level for a few more years. Chung and Branch are more concening.
You brought up Ninkovich and Ryan. They also lost Sheard and Long, who can be considered a starter (combined) as a defensive end, since they often use a rotation.
Hightower is playing defensive end due to need/injury. We are sort down an all-pro middle linebacker in this scenario.
We were hoping to see a second/third year leap from Brown, Roberts, and/or Cyrus Jones.
I agree they will be much better since they have the league’s best coaching staff. However, I don’t think they can just “flip the switch” by improving communication in the secondary. There are a lot of challenges to solve.