You know, I think Nicklaus is right.
My own addled theory (call it "Standardization," "Unnatural Selection," or the "'Major Dummy' Theory") is that the entire process of learning how to play golf and getting better at golf has become standardized.
As a result, the distribution of skill has narrowed at the highest levels of the game: shamateurs + touring professionals. The worst has gotten better but this standardization somehow -- no, I don't understand exactly how, either -- has extinguished the potential for "great" golfers. The potentially-great don't really dig it out of the dirt anymore, they're put on a sort of conveyor belt which squeezes out the stuff which is "flawed" but which could yield greatness down the road.
Like what? Maybe shotmaking (not simply working the ball but "seeing" how to play a round, a hole, a shot), creative genius around the greens, and self-contained mental states. (Their psychologists were Jim Beam and Jack Daniels.)
Watson, Player, Trevino (not to mention every great golfer that came before them): all took a very different path to the top, and that's my point. Would they have turned out differently (worse) had they been put on the conveyor belt of standardized learning? (Which one said, "I never quit in a tournament because I was afraid if I did it once, I could do it again." More to the point: does it matter? More to the point: contemplate a contemporary pro saying this? The closest they seem to come to that these days is to spew pseudo-psychological drivel...)
Two things have enabled Unnatural Selection bias:
1. Technology -- teaching technology drives a relentless "crowding out" of idiosyncrasies in various golf shots and teaches everyone a similar set of fundamentals. I&B advances lower the potential for skill to separate golfers.
2. Money -- ups the desire to make the pros and thus the participation rate (more pro tours + college golf), but *lowers* the desire to reach the tippy-top. (John Feinstein's books are full of Hamlet-like pros bemoaning life on the road away from their family; Mickelson et al hardly bother to show up for more than two handfuls of tournaments ex-majors per year.)
A half-baked theory -- but there's nothing better than taking the raw and serving it cooked!