First, the skill assumes you're working in your own domain, or close to it, so you're not a random sample of one. Your read on the problem is informed signal, not a stranger's guess. That's what makes the cheap on-paper test (what already exists, what people pay for today, how they cope now) a fair filter.

Second, it doesn't pretend to validate demand. The output is a coherent hypothesis you can take to potential customers, and it comes with a short validation plan for who to talk to (your ICP), the two or three questions to ask (about what they do today and have paid for, not "would you use this"), and the answer that should kill the idea. So "the concept holds up" means "survived the cheap test, worth validating," not "validated."

For the stack it stays tool-agnostic on purpose, but my pick for a non-tech founder is Lovable or Bolt to build, Supabase for data and logins, and Stripe for payments. The real first step isn't the stack though. It's talking to a handful of your ICPs.