The Pittsburgh Steelers, despite having gone over a decade without securing a championship, have been one of the most successful franchises over basically any period of time you want to come up with going back to the merger and the common draft era. They have the most Super Bowls, the second-most playoff wins, I believe the most regular season wins, second in division titles. They’ve been very good, and they are still good, even with bumps in the road.
For the fanbase, however, or at least large and vocal segments of it, every season that doesn’t end with the hoisting of the Lombardi Trophy is a failed season.