The problem with dynasties is they disengage the other fans. Sports fandom is built on the lie of “maybe this year”. And the sooner that lie gets shattered the sooner fans disengage. Your NHL list is a great example, while that era saw great players and great play not very many people saw it. That was the era when the NHL lost TV contract after TV contract eventually going a decade without an over the air contract. It took until the Comcast/NBC merger to really fix the TV revenue damage done in that era.
That’s the balance sports leagues need to find. A few teams capable of performing the game at the highest level makes for beauty in the sport (at least when those teams face each other). But it’s bad for revenues. Revenue comes from as many fans being engaged in the season as long as possible. That era of the NHL was enjoyed by fans of the Habs and general “pure” hockey fans (with some windows of engagement from Isles and Oilers fans). But fans that didn’t look beyond their team lost interest quickly during the season. The current NHL world where most of the league is in the hunt for the playoffs until the last month and anybody that makes the playoff has a shot is much better for fan engagement.
I'd make the case that the sport was better off before the pursuit of national TV revenue drove a number of decisions that were idiotic by any objective measure. Perfect case in point: moving teams Quebec City, Winnipeg and Hartford to Denver, Phoenix and Raleigh. The league's core strategy over the last 25 years has been to expand into markets with large populations and almost zero fan interest -- for the sole purpose of establishing a national footprint for TV coverage. That's a disaster in the making, and the number of financially struggling franchises in southern U.S. markets (Phoenix, Carolina, Florida, etc.) would confirm that.
How many people are going to see a hypothetical Stanley Cup finals matchup between the Pittsburgh Penguins and the Nashville Predators? That series would probably have fewer viewers than they'd get for a matchup between Chicago and Montreal -- even without a national TV contract here in the U.S.