Indeed, I don't think email can be reliably used to convey complex topics.

> The problem remains that people refuse to do the reading required for their job.

Communicating effectively means accepting common flaws of people who are unlikely to change, and delivering your message in the most effective way. Whether people are right or wrong or should be fired (as another comment says) is not truly relevant.

I often fail, by the way. I'm not saying I have this all figured out.

Adjusting communication to the audience is a good guiding principle, but not an absolute. There comes a point where no attempt at communication works for a given audience. If the communication must happen nevertheless, then the audience must change, whether through training or replacement.