Every NFL team has high turnover. The average life of a player is something like 3 or 4 years. So having a big portion of the roster change is normal business. Only long standing QB's (Brees, Brady, etc) really contradict this trend.
With the Jets I think there were some expectations that the young guys should step up when the vets like TRich, Faneca, Tomlinson left. That didn't happen. Was it a fault of the character of the young guys (Sanchez, DBrick, Harris, Revis ?). Was it bad coaching not to help the youngsters make the transition ? Was this failure of leadership destined to happen regardless of any other facts ? Those are the questions worth debating.