The subtle lesson, which we won't learn is [astronaut meme] all communication is potentially remote code execution. This isn't a computer thing, it's in the inherent nature of how communication works for us too. You can be more or less careful, but you can't eliminate the problem entirely or else communicating ceases to be effective.
We all go through that stupid phishing training. They give us a list of red flags to help determine if an email is legit.
Then the next day, the CTO sends out an email that says IMPORTANT and the only text body says PLEASE READ THE ATTACHED .DOCX FILE. This is exactly what we were just trained not to open, but its from some exempt C-level who didn't have time to take the training, and all he is now doing is training the employees to open mails that look like phishing.