I don't understand the question in 'Didactic Green'. "Your task here is to examine these bytes for their own meaning, and get the answer from there." What is the byte's "own meaning"? The hex code doesn't have any meaning at all to a human.
The problem with substitution is most of the methods of solving it require you to know what the substitutions for the letters are. If there were some brute force way to try all different substitutions until an answer that made sense was found...