It is cringe because the XKCD guy does not know when to stop. The second part of the comic (the white on black part) makes it worse. The graph is the punchline. But then he keeps drawing, and ruins it.
What’s wrong about it? It makes it clearer why 1. The seating is ridiculous 2. Such frustration is ridiculous. How is the graph the punchline? The idea is the punchline.