And none of those QBs (except Peyton) were bottom 3rd either. In fact they all were top 12 or better in passer rating those seasons. Again, except Peyton.
2012 - Flacco was 12th in PR, the Ravens offense was 10th in points, 16th yards.
2017 - Wentz actually powered that offense for 13 games. He was 4th in PR, the offense was 3rd in points and 7th in yards. Foles just had a Flacco like playoff run in a better offense than Flacco had.
2018 - Goff was 8th in PR. Rams offense was 2nd in both points and yards.
2019 - Jimmy G was 8th in PR, Niners offense was 2nd in points and 4th in yards.
So you actually do have to have good QB play, and no, it doesn't necessarily mean you need a top 10 QB, but that QB probably needs to play at a top 10 level in that particular season. To consistently be a contender though, a top 10 QB is pretty much a must.
While I agree about needing a good QB you can't ignore the defense's impact on a team.
Here is a comparison on the Chiefs 2018 & 2019 seasons
Statistically Mahomes was a better QB in 2018 than in 2019.
2018: 12-4 Record, 383-580 66.0%
5097 Yards,
50 TDs, started 16 games avg 3.1 TDs per game, Point Differential 565-421 = +144,
Lost AFCCG
2019: 12-4 Record, 319-484 65.9%
4031 Yards,
26 TDs, started 14 games avg 1.8 TDs per game, Point Differential 451-308 = +143,
SB Winner
He threw 24 more Tds in 2018. Some of this may be due to his injury in 2019 but he averaged 3.1 Tds per game in 2018 & 1.8 Tds per game in 2019. The Chiefs scored 114 more points in 2018 than 2019.
Yet the Chiefs finished with the same record both years & only outscored their opponents by 1 point more in 2018.
This is because their defense played much better in 2019 (at least in points allowed per game).
In 2018 the Chiefs were 25th in points allowed per game (24.8).
In 2019 the Chiefs were 7th in points allowed per game (18.5).
Like the old saying goes 'defense wins championships' & football is a team sport.