If we're going to really play that card, lets be honest, Wayne and Mario played against garbage goaltending and defenses in their hey day.
McDavid is putting up his numbers against actual goaltending and defensive structure. The 80s and even well into the 90s doesn't hold a candle to how much the sport has changed from about 1996 onwards. There are AHL goalies today that are better than NHL goalies from the 80s especially, the 80s was a total joke.
A Connor McDavid would light goalies like this up like a Christmas tree
Defensive structure and coaching was also significantly worse, a lot of teams basically just played the equivalent of pond hockey back then, trading chances back and forth all night long.