I note that some of you are really into this "size of talent pool" topic. It has some vague interest for me... but very little. I simply don't see it as particularly important. There's no way to determine any "answer" to the question, and even if we did somehow magically determine that, say, 1965 or 2010 was the be-all and end-all NHL of talent-depth... er, so what? It's not going to detemine that Bobby Hull or Alex Ovechkin was the greatest player of all time. It's not going to change who the greatest players were. There are too many other factors to consider.
I will say that, basically, trying to apply today's sporting / pro-sports / salary / cultural-standards to the 1930s or 1950s or whatever is a very poor way to approach the topic. It's just a completely different world. Money is a big part of this, as there simply wasn't the financial incentive for borderline top-talents in the 1920s or 1940s to devote themselves to hockey.
But that point goes both ways: Let's say that we magically determined that 2022 was the peak of hockey talent and competition in the NHL. Does anyone here think that, say, Johnny Gaudreau (for example) is a tougher competition for top spots on rosters compared to top lines in the 1950s and 1960s? I just don't see it. Gaudreau may have competed against a tougher talent pool and may have had longer odds to making the NHL from the outset, but he's also trying to earn a spot in a 30-team League where every club pays big dollars. This means that once Gaudreau was established as a talented player (no small feat, of course), he could sign a lucrative contract (as he did) and now can cash pay-checks the rest of his career while giving 50% effort and avoiding injury (and he's hardly the only player who, consciously or unconsciously, is doing this). The NHL is now a career move
That kind of thing simply wasn't possible in Gordie Howe or Bobby Hull's day. If you underperformed, you were gone almost overnight, and the path back was nearly impossible. It was also a much smaller League, with only 90 to 100 full-time jobs available. I tend to think that in those conditions --- no job security, lower pay, abusive coaches, physical punishment every night --- only the very best and most determined rose to the top.
I think it's pretty obvious that the 1960s was a period when NHL expansion was long overdue and that there was more than enough talent around for a League twice as big (as soon happened in 1967). 32 pro-teams by 1975 was far too many, of course (I would argue it's too many even today!), but I bet if the NHL had (a) been only 15 clubs, (b) allowed 18-19 year old players in the mid-70s, and (c) opened the door easily for Europeans (as the WHA did), a mid-1970s NHL of about 15 clubs would have every bit as competitive as the six clubs in 1966-67.
But again, all this is just speculation. There's no answer to these questions. While it's fun to discuss (sort of), I think once we start getting into racial analyses of the Canadian population in Quebec in 1965 or whatever, we're kind of entering on nutty territory.