It's a shame that some teams never won more than one. The 1985 Bears and the 1996 Packers are my two entries. Both came in a little less edgy the following season and ended in disappointment.
When you look at the other top-tier NFC teams of that era 1983-1990 Era: San Francisco, Washington, NY Giants, with the LA Rams and, towards the end, Philadelphia at a second level, the NFC was so difficult to get past.
Ditka was never an innovator in a decade where he was up against Walsh, Gibbs and Parcells, including some of the all-time great teams (83 Redskins, 84 49ers, 86 Giants, 87-89 49ers -- not necessarily teams that won it all but teams that were already at the top level).
McMahon unable to stay healthy played a significant role but Ditka's inability to adapt after 1985 made Chicago a paper tiger after Super Bowl XX. I always had the sense that Walsh/Gibbs/Parcells would clean his clock late in the season because they simply were better at exposing weaknesses. Ditka just wanted to line up.