We wouldn't do well on these topics, in spite of our rationality, because doing well on these topics requires information, and we don't have any inside track to reliable information.

Yes, there are topics for which most of us don't have sufficient information to write about them or discuss them. However, people with that information almost always do exist. Therefore, we should encourage them to come here and share that information. Maximizing the chance that those people do write here means carefully avoiding things that might deter them, and fear of being seen as off-topic is such a deterrent.