The Pittsburgh Steelers won the Super Bowl in 2008. They made it back in 2010, but lost. Since then, they have a total of three postseason victories and one trip to the conference finals—and not for a lack of opportunity. They have six first-round exits in the intervening years, though one technically was a second-round exit in the Divisional Round because they had a bye week.
There are many reasons for this, including just some bad luck. One of the fundamental concerns, however, is the simple fact that, on the whole, little ever changes. The Steelers stay the course, trying their best year to year, always confident in their plan, but rarely with the resources to make significant additions.