Edmonton's powerplay numbers are the best recently, but all powerplays have went up in the past five years, the past five years powerplay rates of various teams represents itself very well in the list of top powerplay rates since they were recorded in the late seventies.
McDavid hits 150, Kucherov and MacKinnon hit 140 the very next year.
The fact of the matter there has never been a kindler, gentler, time to be a superstar today. They've gotten rid of more obstruction, slashing, hooking, holding, than I can remember. Teams don't really even hit so much, it's all stick checks. To top it off, empty net goals are more frequent than ever, Al Iafrate would be appalled.
Then there is the entire gameplan of loading up top units nowadays, to a far greater degree than before, especially the Gretzky/Lemieux times when depth scoring was way higher, and Edmonton really loads up their top unit.
So when people go on about how shitty the goalies were (yeah they sucked compared to today) or defenses (this one I'd challenge more, a lot teams were more offense focused anyway, and even if you grant teams having better structure today, all these guys can do is stick check, no shadows grabbing the jerseys these days).
Keep the rankings of McDavid only with others in his soft era, it's incommensurable with hockey in the past anyway.