Winning with a bad QB is an exception that can occassionally happen when you have easily the best defense in football (2000 Ravens 2002 Bucs, 2015 Broncos). It is not a tactical plan.
I highly doubt that any of the teams in the league with mediocre to bad QBs have a front office plan in effect that says "Let's just hold on to the bum until we build a defense so dominant that it's compared to the '85 Bears, and win with that".
The Bears are about 9-10 starters away from that kind of defense. We're 1 QB away from having a good QB.