Don't eat the cheese. Competent QB play can elevate a team very well, subject to reasonable other factors, and great QB play can turn decent teams into great / winning ones.
Someone is desperate to use the 'bad team' excuse for failed QB play for a very specific reason. And it isn't pertaining to the Niners or Saints.
Did 4x MVP Aaron Rodgers turn the Jets around? How many playoff games did Matt Stafford win before the Rams? On the flip side, what did Sam Darnold look like before Minnesota?
"Competent QB play" is usually elevated by skill players and scheming and that's why people are questioning if Purdy should get paid as a "franchise QB." As mentioned in the post, good quarterbacks have never made bad teams good. More often than not, when you see a major turnaround, it is usually because of major overhauls. Do we make it to a conference championship with Drew at QB in 2005? The problem with making everything about the QB is it is the most dependent position on the field. Elite teams will beat elite QBs every Sunday. There is a reason Peyton Manning only has 2 Super Bowls and one of them came when he was one of the worst QBs in the NFL.