Same, honestly. I've dabbled in trying to come up with some UI stuff with LLMs, but I'm still not at the point where I'm totally comfortable. At my day job, luckily I have people much more talented than me at design who can provide feedback and guidance. For my personal side projects, I've had some modest success inducing the agent to provide the feedback from a suitable "persona", for lack of a better term (e.g. "Is there any existing standard on how to make this component accessible?", "How intuitive would you expect a non-technical user to find interaction with this?").

I read somewhere that Claude is better at UI than Codex. I haven't tested it yet. I am currently using Codex for a couple of native application projects with Avalonia. The UI isn't really good at all and I can fix it by hand far better than it does with prompts. For example, a table to view database data ended up with huge spaces between rows and columns and it can't seem to grasp how to format a table nicely. So I fixed it by hand, no big deal.

Pick a website you like, and tell claude to use it for inspiration. I do this all the time and the results are pretty impressive and different than what you get out of the box prompting.