100% of Go is estimation. I’m not talking about territory estimation, though this is also a good application of the word. Nor am I talking about positional estimation, though this is also important. I’m speaking of the psychological factor that exists between yourself and your opponent.
There’s a good reason that many people bemoan their ranks, get stuck at certain ranks, and play better in an unranked system. Part of getting stuck is technical, in other words a lack of knowledge. Even when these technical points are factored in, however, ranks are still a psychological barrier (though in this case, not related to estimation).
The real problem with ranks is the estimate or prejudice you make about your opponent, even before the game begins. To play well, one must overcome the overestimate or underestimate you’ve given your opponent and play the moves you think most correct. How easy it is to lose to a 9 or 10 kyu player when at the rank of 8 kyu - even in an even game! This is because you believe they’re weak and play too softly and with too little reading. I can only imagine what kind of psychological barrier being a 1-kyu playing a dan level player (or vice versa) must exist.
And because I brought it up, there exist a number of plateaus starting at the 12-kyu level. I’ve spoken of them in the past, but I’m certain that: 99% of the problem at any barrier is psychological. Certainly there’s some additional skill you need before you can pass the barrier, but this type of learning is small. It’s much harder to: identify that which needs to be learned and apply that which has been learned. The non-psychological step in the middle is (usually) the easy part: processing that which needs to be learned.
One of the things to understand, starting at [about] the 8-kyu level, all increases in ability are from an increase in reading skill. I can’t say it enough… everything involves reading - some are tougher tasks than others (joseki-type reading, mid-game (non-contact) type reading). Counting and estimation are still important, but those tasks pale with respect to raw reading ability.