>>520968853
It's not just that IQ isn't the end all be all, it's that this test only measures a limited domain of IQ, that of fluid intelligence. There's also crystallized intelligence (basically knowledge), working memory, processing speed and verbal comprehension.
These domains have some correlations, but it's not absolute.
Shakespeare would have probably been better at math than the average person, but not a genius. Newton would have been more articulate than the average person, but he likely could not have written the Divine Comedy.