I'm sure everyone has their own tolerance for what is and isn't maintainable :). For me, not knowing what code exists, where it is, how it fits together, and stuffing it all in one main file feels like a recipe for trouble down the road. Sure, I could probably tell the LLM to split the main file into modules and ask it to refactor code etc.

However, from personal experience I'm a lot more efficient when I use LLMs to help with tedious, boilerplate-like code writing but I remain in control over structuring the project so it's maintainable by more than machines only.

I use LLMs every day to write tests for example, it's a massive time saving and I wouldn't want to write tests manually ever again.

I just watched a video https://www.youtube.com/watch?v=eIoohUmYpGI which I think summarize your points here, recommend it to you as well.