For example, the right database schema or the right architecture I could easily see saving you 10x the development effort, but these are the things copilot is least able to help you with.
Am I misunderstanding something here? Or could it be that what you are finding is that your experience is helping you build faster, and this is being misattributed to AI?
I'm building a product as an experienced engineer with 17 years in the field, and the only place LLMs would be useful without slowing me down is writing copy, whereas I would pay for a copywriter, which I will probably do.
LLM making you 10 times faster to build a product (of which coding is like 20%) needs better sources and proof, as it's a ludicrous number, and a whale with billions has access to much better tools than ChatGPT (i.e actual paid humans).
If by building product you mean "create a basic landing page in HTML", sure. But a landing page is not a company, nor a product you can sell.
Speaking from an entrepreneur's POV, AI gives me an unfair advantage with respect to the large whales. It lets us complete projects (specifically, software projects) 10 times faster and achieve things before I had to raise millions to achieve them.
I can't tell if the net negative/positive is + or -, but it's not clear-cut for sure.