There is no set, singular argument.
In football, you have to look at the entire picture because statictics can be deceiving. And there are some teams that would never succeed without the right QB (for example, Cardinals without Kurt Warner, and to a lesser extent, Rams without Warner), and other teams that would have succeeded with just about any competent QB (2000 Ravens, 2002 Bucs).
Somebody like Warner was obvoiusly an elite QB, because largely based on his play, he carried two dead franchises to Super Bowls, and both franchises were dead again with a couple of years after he left. It would be impossible to argue he didn't make a gigantic difference on those SB teams he played for.
The Bucs nearly went to the Super Bowl with the same primary cast of characters a couple of season before Brad Johnson, with Shaun King. SHAUN KING!
The Ravens, obviously, have been a dominant team for the better part of a decade because of their defense. Trent Dilfer had little to nothing to do with that SB win. He didn't even start half the games, ffs. He lost the starting job in a camp battle to TONY BANKS.
Nobody who ever saw Trent Dilfer play would ever call him elite based on his skills, production, or ability to carry a team. It requires only lazy, surface level thinking to conclude a QB is elite based on winning a SB. We've seen mediocre, even below average QB's play for SB winners, and we've seen guys have terrible games and still win.