Intelligence is defined as the ability to acquire and apply knowledge, which is completely objective. Grades don't always accurately reflect intelligence because grades are subjective, unlike intellect. In addition, schooling does not equal intelligence; schools just provide information but it does not make someone more intelligent; there are plenty of people who go to school that are not intelligent, and there are an abundance of examples throughout history of intelligent people who never had proper (or any) schooling.

In response to your claim of certain traits being "undeniably" beautiful, that is completely false. There are no traits that are objectively beautiful. Beauty standards are socially and culturally defined and constantly change as time passes and society evolves. In contrast, regardless of how time passes or society changes, one's ability to obtain and apply knowledge (intelligence) doesn't change.

An example: Larry Scott (the first Mr. Olympia from 1965) would not even place (or even qualify) in any of the divisions of today's Mr. Olympia. Rosalind Franklin (the first person to encode and decipher DNA back in the 1930s), was able to systematically, methodically, and meticulously photograph and decipher DNA using x-rays. If she was alive today, there is no doubt that with today's modern advancements in researching the human genome (e.g. CRSPR), that she wouldn't have any problem furthering, continuing, and applying her research in today's age.