A sports analogy appeared in yesterday's HN thread on this topic: the difference between an average runner and the fastest man alive is less than 50%. The counter argument here is that the measurable variable here isn't really the skill of the programmer but the success of the company (or equivalent). You only have to be best by a small margin to win. If you count wins between me and Usain Bolt he would be more than…
Now there's plenty of space for jokes like do this to C++ and that language is so fat most people won't notice if a random component disappears. Or do this to PDP-8 assembly language or a turing tarpit and the language is so small that one component removal might make it no longer turing complete, maybe impossible to complete the challenge. But generally speaking, yeah, remove a big part or enough small parts and you'll take a 10x performance hit, sure.
Now there's "know" and then there's kyu/dan ranks from go. Too much binary thinking means people who have a correctly applied checkbox don't really know what they're doing, or maybe they do. Thats why its hard to predict.