Genius is a sort of myth. For example, people seem to have the idea that before Charles Darwin, biology was in a dark age without any ideas other than intelligent design or some such. Well, no, Darwin was actually relatively unoriginal in his ideas about evolution, which was already commonplace in biological circles. He really just added a bit of sciency-but-not-quite-scientific rigor and coined the term "natural sel…
That’s entirely unfair. Darwin spent his whole life furiously gathering evidence from everywhere he could and communicating with the rest of the biology community worldwide. If you read any of his books (the most fun, I think, is the Voyage of the Beagle) the constant probing and questioning shines through. The man made hypotheses about everything he saw and tested them where he could, or suggested possible tests even when they were beyond him. The character I see when I read Darwin is a passionately curious, perceptive, insightful, and careful man.
To call, for instance, The Origin of Species, one of the most remarkable presentations of evidence of the 19th century, “sciencey-but-not-scientific” is to project modern standards onto the past. There were certainly other people with similar ideas in the biology community (Wallace for one), but they weren’t anywhere close to mainstream. Darwin’s evidence in The Origin, however, was overwhelming. And It stands up remarkably well today; some parts could certainly use updates after 150 more years of inquiry by many more people with better tools, but it’s mostly very good.