It wasn’t a function of NFC dominance it was a function of dynasties. Half those SBs won by two teams. The NFC as a whole wasn’t that dominant, cross conference was close to 500. But there were the mighty dynasties that were just plain better than everybody else. Outside of those dynasties the NFC wasn’t that great (especially not the NFC Central, home to the twice annual Bay of Pigs games where the incredibly awful Packers and Bucs played terrible football twice a year). That’s what everybody forgets about that era, they remember the dynastic teams playing great football in their playoff matches, they forget that the rest of the league mostly was terrible and played unwatchable football.
Dynasties are boring. Just look at the NBA. 2 years ago I said the only way we weren’t seeing a rematch in the finals was if Lebron or Curry got hurt, with an outside chance of the Spurs figuring out the Warriors. Last year I said the same thing. I’ll go even further and say that the only way it’s not Warriors Cavs NEXT year is if Lebron or Curry get hurt with an outside chance the Celtics figuring out the Cavs (forget the Spurs, they’re done). The entire NBA season and most of the playoffs have no meaning to the league. And they’re unwatchable because there just isn’t the talent on those other rosters.
This has always been the problem with the NBA though. The team with the best player is always going to be one of the best teams. If the best player is teamed with another all-star, they are almost certainly going to win the title.
Magic’s Lakers were in the Finals 9 times. Most of the time, that march to the Finals was a cakewalk.
Bird’s Celtics went 5 times, mainly because the East had two other great teams - Doc’s 76ers and later Isiah’s Pistons.
But if you like any team other than the Lakers, Celtics, Sixers, or Pistons in the 80s, what were you really doing with your life?
Basketball at all levels just seems to lend itself to dynasties better. Lebron is literally 20 percent of the Cavs. Tom Brady is 4.5 percent of the Patriots.
Dynasties are boring only if they are built on some kind of advantage in the sport that pushes some teams to the top and eliminates others from any reasonable chance at contending. MLB was like that back in the middle of the last century, when teams from the larger markets dominated the game and many small-market teams were no better than minor league franchises.
I don't think a dynasty built on a solid organization, great personnel decisions, and a great coaching staff hurts a sport at all. A lot of hockey fans will tell you that the first 25+ years of the post-expansion era in hockey (roughly 1967-1994) was the absolute heyday of the National Hockey League -- and that era was dominated by dynasties.
The era from the 1967-68 season to the 1993-94 season covers 27 seasons, and there were only two Stanley Cup champions in that era who only won a single title:
Montreal (10)
Edmonton (5)
NY Islanders (4)
Boston (2)
Philadelphia (2)
Pittsburgh (2)
Calgary (1)
NY Rangers (1)
That era saw some of the greatest players the game has ever seen, and included team and individual performances that may never be matched in the NHL again. Notice that half of the teams on that list would be considered "small market" teams today, and most of those small-market teams faced financial troubles later on that threatened their existence.
I agree with your assessment of the NBA, but that organization has a whole different problem. Basketball is a simple game with a smaller cohort of players than any other sport, and it's easy for a team with two great players or three very good players to dominate the game. I don't know what has changed in the NBA in recent years (I haven't watched a basketball game in years), but as recently as the 1980s there were a lot of exciting playoff series in the early rounds even though the Celtics, Lakers and Pistons seemed to win most of the titles back then.