No, you don't get an understanding of how the game works by learning individual things that only apply in specific scenarios.
You get an understanding of how that individual thing works in that specific scenario.
No what you want to get is
why these things work and particularly why X is better than Y. If you play enough, the "why" question just becomes innate. I've seen people tell me I'm wrong about things they actually have done when playing me. If you want to understand the game, why is by far the more interesting question. This doesn't make you a stronger play particularly fast, but you have a much better understanding of things. Much like how chess problems don't give you a huge leg up in competitive play but do allow you to understand the game better.
I stopped reading the Counterfeit/Venture thread when the posts got tl;dr, so I'm not sure what kind of stuff was discussed there, but I'm sure that learning about "when cards dig for stuff, it's good to build your deck in such a way that they will hit stuff you want them to hit" is way more useful than learning about "Counterfeit is good with Venture".
The latter is a specific instance of the former as you are I'm sure aware. However, no one reading the board is a moron and we all can learn inductive or deductive reasoning. Inductive reasoning is typically easier for people to grasp and far more rapidly integrated (hence part of the reason humans use so many analogies in argumentation); but the board may be skewed. Nobody thinks learning every possible synergy between any two cards is a good idea, but the skills find such synergy as exists can come either top down or bottom up. In Dominion the former has the advantage of being "applicable" more often, the latter has the advantage of not get edge cased to death and actually can be discussed in concrete or even quantifiable turns.
Regardless, the most efficient course of action isn't to read anything, it is just to go play more and observe your opponents when they beat you.
Also, even though we are all Wandering Winder, elite players are, surprisingly enough, actually not a hive mind. Everyone has their own playing style and it influences things, and some elite players are simply even better than some other elite players and that also influences things. I remember a lot of games where I went for a different strategy than my opponent, and one of us won because we both implemented our strategies fairly well and one strategy was better than the other. I don't remember a lot of games where I went for a different strategy than my opponent and felt that the winner had the worse strategy, but played it so much better that he won anyway.
Ehh its pretty hard to disambiguate "shuffle luck" from tacit timing and end game skill. When both players get up in skill, the changes we are talking about are likely less than flipping a 45-55 split to a 55-45. You'd have to squint hard to see that in a single game. We hear about the epic things (like buying an Herbalist for $11 and that being the right timing), but a lot of games have small timing choices that have a non-negligable impact on score, often a larger degree than the objective strength of the strategy. I mean consider Big Money games. If we are both playing BMX then whoever picks the better X should win ... but we had to go through a fairly extensive optimization of the end game. If you are better and deducing the point when to start swapping into Estates or when to get an extra $8 gold and I'm not doing end a solidly end game timed BM you can win with a lot weaker X's. If timing skill didn't matter you couldn't have sims get noticeably better with more in depth timing routines.
The majority of time, I'm probably going for the same strategy as my opponent, but there are times when someone tries out something new. It might be the case that there's stuff that you would try out, but an elite player wouldn't, and then we don't have data about elite players trying it out, but I'm not buying it that there's any major reason for this other than that the strategy actually isn't very good and elite players can see it without even having to try.
The odd thing is we see pretty big swings still year to year with different card rankings. This shouldn't be happening if the game is revolving around accurate picking of card strength. Changes should be relatively static and there should be convergence in elite player thought on exactly what the strong cards are. It is only where players have different tacit, tactical skills where you can have divergence.
Given that elite players are divergent on their card rankings, I think it is a safe bet that a big portion elite play (particularly given your admittance to playing a lot of mirrors) is timing skill.
If you pick a strong card like Scrying Pool and ignore it for 100 games, you will probably lose pretty much all the games where the card is on the kingdom. Which is not that many. And if you would have lost somewhere around 50% of those games anyway, it's just natural that you won't lose that many extra games because there aren't that many extra games that you could have possibly lost in the first place. Maybe there's one or even two games where ignoring Pool is actually correct, but most of the time, it won't be, and if you ignore it regardless, there's just no way you're ever winning the game against someone who doesn't.
You can safely ignore it much more often. Take Rebuild. In ~1% of Pool Games you will also have Rebuild. I can't think of a single Rebuild board where Pool is a good buy. In about .1% of Pool games you will have Hermit/Market Square which is very often going to beat Pool handily. In maybe .25% you have a viable pin deck. And so on and so forth just for the two card combos.
My guess is that you can safely ignore Pool twice as often (which is
still saying Pool is exceedingly often a high power buy), but again my point isn't that some elite player is horrid at Pool. It is that even if he is relatively bad with Pool, his experience wouldn't be able to show it. You could drop 10% of your win rate with a certain card and you still wouldn't see it unless you have extremely strong recall and a good statistical sense for these sorts of things. Differentiating card strength (what people played), tacit timing skill (when/how they played it), and shuffle luck is extremely hard.
Again, if you just want to be an elite player, skip the boards. Go play or maybe watch several games. You will learn far more for your time.