If you wanted to generate poems with GPT-2, you'd need to have a lot of poems to fine-tune GPT-2 to get reasonable results.
With GPT-3, you use few-shot learning instead (without the need to do gradient updates with each example)
The paper is long and filled with how it stacks with models like Grover and T5 and it does well... given that this is a 175 B param model (relative to Grover/T5's 1.5/11B param models). This shows that even with these huge models, smaller models can outperform them in certain instances with lesser param models.
Also I think they did a good job with explaning the ethics and morals around what models like these mean / what biases this has.