Team A is still in its prime. Kane might be playing the best hockey of his career. Ovechkin is the reigning Conn Smythe winner and the Richard leader...again. Bergeron is still the best defensive forward in the league and scoring better than he ever has. Stamkos is playing his best hockey since his broken leg. Crosby is playing arguably as well as he has since 2014. Tavares might score 50 for the first time. Wheeler is 2nd in the league in assists.
As well, the fact that the 2nd group might be having slightly better seasons doesn't make them better. It's not as if players like Point, Rantanen and Aho have proven this is their norm, and off years for guys like Hall and Giroux, who won the Hart and finished 2nd in scoring last year doesn't mean they've actually regressed. Variance happens.
Besides, the difference in production between the two isn't very large. Combined, the two teams stack up like this:
GPG
Team A: 0.44
Team B: 0.49
APG
Team A: 0.73
Team B: 0.77
PPG
Team A: 1.17
Team B: 1.26
Over 82 games, that would give the average Team A player a pace of 36 goals and 96 points, and the average Team B player a pace of 40 goals and 103 points. That's a pretty minor difference when Team A is better defensively and has an edge in experience.
It's not an off year for Hall. Hall winning the hart was the outlier year of his career. He hasnt proven that's his norm anymore than the guys you've listed. Stamkos might be playing his best hockey in a while but hes fourth wheel to Hedman, Kucherov, and Point. None of whom proved anything in last years playoffs...
I doubt Tavares will score 50, and the guy driving the offense for his line is on team B. Pastrnak is the weak link for team B, but hes a scorer so I'd have him with McDavid, not that being the weak link here is a slight. Team A has a couple themselves.
Not sure how much bigger of a sample size you need for the MacKinnon Rantanen combo... we've seen their chemistry for 1.5 years and they've been torching the league. With Barkov, forget about it... I also dont see how Crosby is playing his best hockey since 2014 when hes 10th in scoring (23 points back) and 8th in ppg. His defense does not bridge those gaps... hes not playing defense like peak Pronger...
An average of seven points is not that minor when you realize team B is starting their prime and A is beginning to exit theirs. Experience and defense are quite overrated when talking about forward cores like this. These would be the absolute most potent offenses to ever touch the ice in the history of the game...by a lot. Teams like this would bring back the 80s against the average NHL teams, even if they were playing against peak Hasek.