This is a separate thing. It's not about imperfections: most of these websites work just fine. It's that everyone gets the same LLM, and if you just ask "hey LLM, make me a website", you get a very similar product. Eventually, people learn to recognize and hate that aesthetic because it's overused.

The exact same thing happens with LLM writing. There's nothing wrong with "it's not X, it's Y", but I not do my best to avoid that phrasing because it's tainted by AI slop. I did use it in this reply and part of me is bracing for the accusation...

You can overcome that by exercising more control, but most people don't know they can, and if you start micromanaging an agent, it slows you down and negates much of the speed advantage.