"Why haven't more EAs signed up for a course on global security, or tried to understand how DARPA funds projects, or learned about third-world health? I've heard claims that this would be too time-consuming relative to the value it provides, but this seems like a poor excuse. If we want to be taken seriously as a movement (or even just want to reach consistently accurate conclusions about the world)."

This one worries me quite a bit. The vast majority of EA's (including myself) have not spent very much time learning about what the large players in third world poverty are (e.g. WHO, UN). In fact you can be an "expert" in EA content and know virtually nothing about the rest of the non-profit/charity sector.