I've never understood this argument that the competition was weaker in the old days. Makes no sense to me. If anything, I think the opposite is true.
Let's look at it this way -- Is half the NHL Canadian now, or roughly so? So, that's 15 or 16 rosters of Canadians only, which is far more players than were playing in 1965. So, just that makes the old-days look more competitive.
From WWII to 1967, there were six teams of Canadians only. But actually the rosters were smaller in those days, so six teams then is probably like 5 teams today. So, that means in a five-team all Canadian NHL, about 250 of today's Canadian NHL players won't be good enough to play.
In other words, make five balanced teams using today's Canadian players -- each would have two 'All Star' first lines, for sure -- and that's your same strength of competition in 1965.
So, yeah, Ovechkin and Malkin and Karlsson and Lundquist are out of this League, which might help Crosby's and McDavid's numbers. BUT, in this League Crosby now faces only five teams all season, each of which knows him intimately, and each of which has two All Star first lines. It's like the playoffs all season. Then, remember those 250 Canadian NHL players of today that Crosby and McDavid face? Those 250 players are no longer good enough to play in the five-team NHL. The strength of competition has gotten way tougher by reducing today's NHL to a five-team all-Canadian League.
Now, clearly there were periods after 1967 when the NHL became briefly 'watered down' or had a preponderance of lower-level teams -- notably roughly 1968 to 1975, with briefer spikes around 1978 to 1982, and 1991-1993, etc. But I personally think if today's NHL were about 24 teams, it would be just right.