I think basically AI posters are bad because when given freedom to the model (which is what people will do when just asking "make me a poster for my coffee shop"), the model will always tend to do the same design style. So yes, as this article says, with better prompting you CAN get better results. The other problem I think is tool calling, because when prompted for a poster, ChatGPT will definitely use image generation, when it should be generating some html and css + some image assets and then presenting the user an image or pdf.

I think the tendency to go for image generation always might be related to token costs, designing with Code & adding some generated images to the mix should be more expensive than just image generation.