In my life time there have been 3 Steeler Eras, The Noll Era, The Cowher Era, and The Tomlin Era.
Each era has had their peaks and valleys, many more peaks than long valleys.
Each era has had a different starting point on the timeline, each starting point had different challenges, each coach met those challenges with great success.
Each era on the timeline had teams that were built and rebuilt. Each era on the timeline (Noll,Cowher,Tomlin) had good drafts and bad drafts. Each era had a HOF QB.
NFL history dictates that a HOF QB is a necessary ingredient to win a Championship, not every time, but most certainly nearly every time.
A teams chances of hoisting the Lombardi are greatly enhanced with a HOF QB. However a HOF QB does not guarantee anything, the sum of the parts are what makes a championship team. If the Sum of The Parts is inadequate the team will fail. The record of a bad team could be 8-8 with a HOF QB, and 6-10 with an inferior QB. I use Big Ben as an example, as he has never had a losing record.
A couple of years ago at a conference that I was attending Terry Bradshaw was a featured speaker, I can see why he drove Noll crazy. He didn't prepare, he just winged it, the result was an embarrassing speech that was mostly a meandering mess with no point at all, just TB trying to tell funny stories mostly about his hands and Mike Websters butt.
One of the "funny" stories he told as how the Steelers had just resigned Ben Roethlisberger and Terry just could NOT understand why. The point is before he criticized Tomlin he was criticizing Ben. Just as he criticized Noll, just as he criticized Pittsburgh and its fans.
When it comes to grading out coaches Terry Bradshaw is about the last person I would got to for comment. He rarely ever listened to them.
But Thank you for your part in 4 SB's TB! The sum of those parts were as exceptional as they were legendary.