There is nobody that can deny—successfully, anyway—the tremendous amount of accomplishments that the Pittsburgh Steelers as a franchise have to boast about in the modern history of the NFL, since the merger that was finalized and put into action beginning with the 1970 season.
No team has won more games than they have in that span. No team has gone to the playoffs more often, or won more division titles, or won more playoff games, or participated in conference championships, or, most importantly, won more Super Bowl trophies. They are the only team in NFL history who can claim to have six Lombardi trophies in their display case.