The biggest problem in my view is:
It's not editable by hand. There is no production data I could open in InDesign, Illustrator or Photoshop (Layers) and change things to my or my clients liking.
You can certainly ask ChatGPT for a poster, then ask it for a collection of assets with transparency, so you can composite them as you wish.
It does take away from the "smash out a poster in 10 minutes" that a harried PTA volunteer wants, though.
I suspect the tool to do this as a one-stop shop is coming very soon, though.