The Steelers have been great before Big Ben, and won the Super Bowl when he wasn't playing elite. They also managed to get a new coach and then go back and win another. The Ravens won it with Trent Dilfer, then again with Flacco, and are now one of the best teams in the league with a non-traditional QB. Packers have two Super Bowls in recent memory with two QBs and multiple coaches, and find themselves in the playoffs every year. The Seahawks were great with Matt Hasselbeck and have found themselves consistently great again with a new coaching staff and QB.
Even the Patriots were in a Super Bowl and playoffs just a few years before the Brady-Belichick era.
It's silly to handwave away those franchises' successes as "just getting franchise QBs." I want a consistent shot every year, not some shot in the dark team once a decade.