I was referring to the high degree of opening memorization and the search for new variations which give you an edge in competition chess, not to the search for the "perfect game" concept.
Oh, sorry. I'm glad to hear that. In that case, I can agree that memorization of openings is important -- but only in the same sense that, say, learning to play scales is important for a musician. "Key" only in the sense of "fundamental".
For players who reach what you are calling "elite" levels, remembering openings (along with their various quirks) requires no more effort than it does for the average person to recognize the face of a familiar old friend. The point at which things begin to turn on "new variants" is, I would argue, the point where the opening ends and the middle game begins.
Then it becomes more about recognizing familiar
patterns and how they relate to the current (and almost certainly unique) position. But that's not really a matter of
memorization, at least not in the ordinary sense. Is it? I mean, how
do you recognize a person's face? Are you fully in touch with that process? You might say that you have that person's face "memorized", but that doesn't sound quite right, does it? It implies a level of effort on your part that you probably don't really deserve credit for.
I fingerpick a tune on the guitar, and somebody says, "Hey, how are you doing that?" -- and I usually can't answer in terms of which finger is engaging which string at which particular time, because I don't notice that so much anymore, and when I try to slow it down so that we can investigate, I often can't do it without screwing up.
I think chess gets like that. The experienced player is better at noticing the things that are worth noticing, and he probably couldn't tell you how he does it other than just: "experience". Perhaps even more interesting is what that implies, which is that he's also better at ignoring the things that
aren't worth noticing -- and the things he ignores, he ignores so completely that he isn't even aware that he's ignoring them. We all do that. Whether our experience was gained on a chessboard, or a freeway, or the Arctic tundra, we ignore most of what's going on, most of the time, and we don't realize we're doing it. And if we fail to notice the things that are important, we may end up dead.
"Noticing the things that are worth noticing" might even be a reasonable working definition for "critical thinking". But the OP's question has to do with learnability, and with portability from one environment (the chessboard) to other environments, and I'd have to rate that as poor -- unless perhaps (as I said earlier) to the extent that it inspires one to undertake examination of the flaws in one's own approaches to problem solving in general.