You seem to think design is mere flourishing, nice colors to make something pleasant to look at, but ultimately superficial and useless. I would strongly object to that--visual presentation can carry a lot of additional information, and improve the transmission as well. Giving more people the ability to present information well leads to more efficient communication, which I wouldn't just dismiss this easily.
But there isn't any extra information in AI posters. It's necessarily either something that can already be conveyed in writing (that is after all, what they're prompted in), or something the AI pulled in based off of the text unintentionally, at which point no actual information is being conveyed by the added visuals.