Regardless of whether Tomlin is a great, good, average, or horrid coach, There is very little chance he ever wins another superbowl with the Steelers... change is often a catalyst to coaches growing and expanding out of comfort zones... the guy has been here almost 20 years... he is stagnant.
The areas he has to improve on to win in the current era he simply doesnt need to, because he is too comfortable.. no head coach in any sport should stay in a place over a decade... its just not a great way to win...
His ideas of how to run an offense or defense are stagnant. But I think the old thought about coaches getting turned out by players after too long at one place may not be applicable anymore with the way rosters turn over today.
Its not just tuned out coaches
Lets say coach A is really good at building a D, and knows wrs and qbs, but he really sucks at oline scheme, so he moves on and a guy comes in who is an offensive guru specializing in blocking schemes and is less great with D
Well coach A built up the D, and got a bunch of undeveloped talent on O... coach B gets tge O turned around while the D is still good and has early success
Now eventually that team will likely end up with a solid O but D deficiencies... at that point you find a coach that fills those voids...
I mean take away Belicheat who was in his second hc job, btw, and Reid( who had to reinvent himself away from Philly) ... and most SB winning head coaches are within their first 4 or 5 years with a team...
Hell, Cowher bucked the trend, but only by completely changing his offensive philosophy in the playoffs in 05...