You keep bringing up John Harbaugh and Jackson so lets go with that.
Lamar Jackson and John Harbaugh are 2-5 in the postseason with losses against a variety of QBs (Philip Rivers, Ryan Tannehill, Josh Allen, Joe Burrow, Patrick Mahomes) and wins against (Ryan Tannehill and CJ Stroud), do you think the Ravens should have fired John Harbaugh after 2 straight playoff losses? 3? No? I'm gonna guess "because hes a SB head coach"?
Prior to Jackson, Harbaugh lost 4 straight years in the playoffs to the likes of Roethlisberger (Tomlin), Peyton Manning (Caldwell), Tom Brady (Belichick), before finally winning the Super Bowl in 2012. Which year should they have taken the big swing and not settled for being a loser and fired Harbaugh?
Then Harbaugh subsequently didn't make the playoffs 4 out of the next 5 years after the Super Bowl win, and got beat again by Tom Brady in 2014 where Harbaughs defense allowed Brady 8/9 for 72 yards on the final drive. You'd call that a McDermott collapse and 2 years of not making the playoffs would have Bills fans all out against McDermott (I think if we missed it just one time) but here we are talking about the Ravens and Harbaugh being better positioned than the Bills.
Coaches lose in the playoffs. In the last 20 years theres only like 10 that haven't given Belichick and Reids god forsaken dynasties.
Change for the sake of some mystical SB winning HC is terrible in my opinion and is the quickest route back to less than mediocrity for the Bills.