[mulvya]

Of course, that isn't quite true. If the result or outcome of an actvity is publicly observable or measurable, then a secondhand sense of judgement can be developed.

[anamax]

There are multiple definitions of "good at {something}".

For example, the n men in the last men's 100m Olympics sprint were not the n men with the best sprint technique. (Some were on both lists, but some weren't.)