So in the other camp you have seasoned engineers who will have a 5x longer design and planning process. But they also never get it right the first several iterations. And by the time their “properly-engineered” design gets its chance to shine, the business needs already changed.

Because this is the first pass on any project, any component, ever. Design is done with iterations. One can and should throw out the original rough lynchpin and replace it with a more robust solution once it becomes evident that it is essential.

If you know that ahead of time and want to make it robust early, the answer is still rarely a single diligent one-shot to perfection - you absolutely should take multiple quick rough iterations to think through the possibility space before settling on your choice. Even that is quite conducive to LLM coding - and the resulting synthesis after attacking it from multiple angles is usually the strongest of all. Should still go over it all with a fine toothed comb at the end, and understand exactly why each choice was made, but the AI helps immensely in narrowing down the possibility space.

Not to rag on you though - you were being tongue in cheek - but we're kidding ourselves if we don't accept that like 90% of the code we write is rough throwaway code at first and only a small portion gets polished into critical form. That's just how all design works though.