So I had this problem while I was designing the landing page for month17.com (disclaimer: that's my domain). What worked to not let it look like complete AI slop was using other landing pages that look good as "inspiration" for the model, through providing screenshots which yields sufficient results, in my opinion.

it looks identical to god knows how many other sites and also uninteresting for the same reason. How would catch attention of a customer? With a card slightly rotated over another? That's abysmal

I would be curious as what you would consider an example of good design, then I can see how far an agent gets with that. In any case, contrary to what you might believe, this landing page does convert pretty well.

as you said it is underdetermined and about taste.declareting needs and wishes as a frame then it could be more desired output.

You might use Figma which is a specific design tool based on AI. There is a free version. It gave me enough to get some ideas on how to redesign part of the site I was working. Canva also has an AI design assistant. There are some specific tools for design with AI built into them.

what's a feedback flywheel?

Each iteration produces some visual result. Which must feed the next iteration loop. I have tried 3 trivial scenarios - a) rasterize HTML and transduce into text using Visual AI model b) AI text model reads DOM c) You share it with designer, designer converts them into text instructions.

Visual AI samples and doesn't enumerate problems, bad at global consistency/invariants Raw DOM - text from DOM is low SNR proxy for visual state with Designer - slow loop