SB era (1966-2023), QBs that have been considered Great or Very Good which is better than just Good, that never won a SB as a starter:
The list
Fran Tarkenton - great
Dan Fouts - great
Dan Marino - great
Jim Kelly - great
Warren Moon - great
Ken Anderson - very good
Danny White - very good
Randall Cunningham - very good
Boomer Esiason - very good
Michael Vick - very good
Donovan McNabb - very good
Steve McNair - very good
Andrew Luck - very good
Cam Newton - very good
Philip Rivers - very good
Matt Ryan - very good
Jalen Hurts - very good
Joe Burrow - very good
-All of these QBs at least started in a Championship Game or SB but just came up short of winning it all.
The problem, no. A part of the problem, most definitely.
Minshew's play can be classified in a lot of ways. I'm not interested in scapegoating him, he actually did a pretty good job of filling in as the starter; I'm also not comparing him to anyone else, including Richardson. But to keep it as simple as possible, Minshew's limitations definitely held the offense back at various points of the season. We saw his ceiling, we know what he can do and what he can't do. It's really great to have a backup like Minshew. It's not so great to have a starter like Minshew for almost the entire season.