What gives it away?
Also, I want to expunge the word "shape" from my vocabulary at this point. I think I'm developing a nerve twitch just reading it.
But imo it's not a bad thing. Most sites looked like shit in the past. The content is usually where I focus my changes when dealing with LLM generated HTML. And if I want it slightly less LLM flavored in terms of design I just pick a random design system to tell it to use. Apple HIG, IBM Carbon, etc.
Usually just picking your own palette, a design system, and making it remove all the stupid details it decides to add will improve your end result by a lot.