Not my experience. I have large production apps that I'm able to maintain just fine with thousands of lines of JS.

Depends how you set it up. Like any other project I guess. Funny enough, if you are able to produce maintainable code with an llm you could aswell lead a team of humans. LLMs shift your focus on project management and architectural choices.

I let the llm write components which are independent to each other. This works great and keeps everything clean. The times that llm would only generate unmaintainable code are long gone with OPUS, Fable and sol 5.6