> I have seen way too many startup founders delude themselves into building more and more for months without a single conversation with a real user

This has been a problem since the beginning of tech startups. I worked in a dot-com in the late 1990s. Lots of investor money. New offices. Hundreds of employees. The product was well thought out, fairly well built, and it worked. But they had no customers. It's even in the same market niche as products that today have millions of users, but those folks weren't ready for it in 1999, at least not enough of them and quickly enough to matter.

Building something quickly is only a small part of what it takes to have a successful startup. You must solve a problem for people who are ready for your solution and willing to pay for it.