I went all in on Lean Startup, I thought that it explained why I'd not succeeded with my last startup. I built websites, drove traffic and built a mailing list

I went all in on Lean Startup, I thought that it explained why I'd not succeeded with my last startup. I built websites, drove traffic and built a mailing list. I went out and did customer interviews just like they tell you. But it wasn't getting anywhere. I finally had an aha moment when a guy I'd interviewed told me he was teaching Lean Startup at the local university. He said I wish my students were half as good as you with the interview. Then he proceeded to tell me that my idea sucked. FWIW Lean Startup boils down to one thing - does the problem exist and are people willing to pay for it to be fixed. Do anything more, delay writing code and you're wasting your time. If you show them screen shots or anything else you will induce false answers. Oh and read the Mom Test so you ask the questions correctly because for most entrepreneurs it is counter-intuitive.