I do agree that winning a SB is not really the best measure or metric on how "good" is an individual QB. There have been good ones that never had an opportunity, and meh ones that have a ring. Consistent playoff wins in an annual basis is a better indicator, IMO.
Going to push back to an extent, though.
Using the phrase "it takes everything to go right" implies luck is the driving factor. I do not believe that to be the case over the course of multiple seasons.
There's a reason Brady is the GOAT, having done it multiple ways with two different teams. There's a reason PM has 3 rings in 5 years. It isn't all luck.
As far as a Marino/Montana comp?
Marino certainly had better physical tools. I don't believe he had even close to Montana's anticipation, command and understanding if the scheme as a whole, or the discipline to employ it if he had.
I do believe Montana teams had a far more innovative and adaptive coaching staff on both sides of the ball. If we are being honest here, what does that imply about Shula?