[Rioghasarig]

If he didn't deliberately to make DALL-E look bad than he did it out of ignorance of what DALL-E's strengths and weaknesses are. Your evaluation of what is "simple" and what is "more complex" aren't in line with what DALL-E is capable of.

DALL-E isn't good with symbols like letters and numbers. It can't do even very much logical / mathematical reasoning. So a graph is one of the worst choices.

What it can do is make aesthetically pleasing images that match basic descriptions. So there are more "complex" images that DALL-E can produce than basic graphs.