What makes a winemaker good, and others not? Is it nature or nurture? Many years of winemaking experience have humbled me to the point where I have no illusions regarding the origin of wine quality, and where I have a much better grasp on the influence I have on a wine. My guess would be that if you have stunning grapes, you are 80% there, with the winemaker being able to add another 20% to the total quality that is locked into the grapes.
On the other end of the scale, if you have very mediocre grapes, a winemaker will be able to add, and manipulate the quality of the resulting wine to add maybe 80% to the quality of the final wine. My theory could be illustrated as follows.
As humans our evolutionary process has tried to equip us with survival skills, that amongst others include tools to learn from the environment, but inadvertently, we see patterns and relationships where there are none. This condition known as Apohenia, make us correlate, totally unrelated criteria.
A common bad correlation would be to say that good winemakers inhabit some regions more than others. Good grapes do occur in certain regions more than others, which might be more correct. Some people think that men make better winemakers than woman, but then how many woman winemakers are there, how many chances have they received?
One certain bad correlation often made in interviews is that an extrovert personality correlates with winemaking skills. The personality profile for the ideal technical winemaker, would normally exclude this profile. People would often prefer to vote for somebody in an election because he is a good speaker, or looks the part, rather than on merit. If my theory is correct, and you have stunning grapes, you do not need a very good winemaker, you are 80% there anyway.