No, the answer is that there is a limited number of scientists and a limitless number of research directions. This doesn't have to be correlated with brilliance. In fact, it can be easier to research some of the less popular paths because there is less competition and more low-hanging fruits.

Fine. The more accurate word would be "advanced" instead of brilliant.

You're arguing semantics like a Humanty's major. Your exact definition of "advanced" or "brilliant" have barely any relevance to the topic at hand.

There are so many gaps in our knowledge, it's ridiculous. Go look for papers studying how to kill the eggs of canine roundworms (e.g. in veterinary settings) or whether surgery is an effective treatment for exotropia. The literature is SPARSE.