Gus Frerotte comes to mind. Tom Brady's first SB comes to mind. Ben Roethlisbereger's first SB comes to mind. Those guys might not be "meh" now, but they were early on. Eli Manning is not exactly "meh", but he sure as hell isn't steady. He just got hot at the right time. And I don't consider Flacco any better than the 2011 version of Schaub. And of the guys who made it to the SB but didn't quite pull it off, Jake Delhomme and Rex Grossman sure aren't superstars. Hell, Delhomme came really close to being on the list of winners. Then there's Kerry Collins and Chris Chandelier.
There's no doubt that the NFL is a passing league, but that also means you need people to get after the other team's QB and defend. Russell Wilson is a pretty good young QB, but he didn't outduel Payton Manning - the SEA defense did. It's still a team game.