In that last 20 years, only 5 teams have won a Super Bowl without having an elite level quarterback (Hostetler, Rypien, Dilfer, Gannon, Eli Manning). All five of THOSE quarterbacks made it to the Pro Bowl at least once, with Rypien and Gannon doing it in the year they won the Super Bowl.
The other quarterbacks are Hall of Famers (Aikman, Young, Elway), future Hall of Famers (Favre, Warner, Brady, Manning) or likely future Hall of Famers (Roethlisberger, Brees, Rodgers).
If you want to win a championship, you need an elite QB.
Brady, Manning, Toethisberger, Brees and Elway all had great offensive Linemen in front of them. If a team needs an elite Quarterback to win a Championship then a team needs an Elite Offensive Line if they want an elite Quarterback.