My problem with LLM web design is that it adds a lot of useless stuff all over the place. GPT-5.x is particularly bad for this. If it makes e.g. a dashboard it includes a ton of figures and bits of text all over the place that mostly just say the same thing twice. But of course this is not really an innate problem with the architecture and will probably be sorted out soon, and you'll get good results if you come up with all the copy first and then ask it to make the site.