While your observation is correct - I suspect you'd find a ton of fans who love that almost every team is 'in the race' all season long and there are all kinds of battles of playoff spots. Very few teams in the NHL truly rebuild and most are 'going for it' every year as all you have to do is 'get in' and you have a shot at winning the title (unlike the NBA, where 6th thru 8th seeds are easily eliminated in the first round).
That system has given teams incentive to try and win every year. The cap floor forces teams to spend money and get better, while the ceiling really is preventing dynasties. I mean in a vacuum, I probably prefer seeing different teams win every year (personally, I'm a bit tired of seeing GS or Lebron in the NBA, Brady/Pats in the NFL, Crosby/Penguins in NHL, Dodgers/Astros/Yanks/Red Sox in MLB) and in a vacuum, playoff races are much more interesting than following an MLB team that's 'out of it' by June (or were never in it at all like the 2019 Jays). Over the long run, are dynasties better for the sport? I don't know. Sure I'll remember the dominant Brady lead Pat teams for the rest of my life and I won't remember the year the Blues won the Stanley Cup...but honestly, who cares? Does that type of history have a tangible impact on the sport? I don't know the answer to that, but my guts says no.
Those complaining that MLB is boring because there's no playoff races, lots of teams tanking, no incentive to winning should be careful what they wish for.