You attribute this to a lack of cultural evolution, but the problem is that wacky ideas that might be right are frequently difficult to discern from outright pseudo-science.
The idea of "cadaverous particles" in fact appears to be at least partly a bit of pseudo-science: There are no such things. Semmelweis had accidentally stumbled onto germs, but he didn't know it, and therefore his reasoning was flawed even if it gave a correct result; If the doctors stopped dissecting corpses, that would have reduced things just as much as the mid-wife ward. If he'd understood why washing hands actually worked, he could have had the mid-wives do so as well and save many more lives.
I also don't think it's correct, at least using the Semmelweis example, to say that "we haven't culturally evolved". Semmelweis's failure to spread what he learned was at least as much victim of his own personality as anything else: "Semmelweis was not very tactful. He publicly berated people who disagreed with him and made some influential enemies".