With that said, the article is less relevant mainly because different products and startup ideas have totally different ways of validating them.
(eg How do you validate a new CRM SaaS product side project vs. validating starting a company like Hyperloop vs starting an "Uber for skydiving for dogs" company...? Not the same things at all.
Some folks may disagree and of course this is not always possible (usually due to budget?), but in my experience if you are serious about a product or startup idea then hiring a professional to do proper market/customer research is worth the cost, just as hiring a lawyer to do initial trademark research and handle corporate paperwork (employee docs, investor contracts etc.) is worth the cost.
Hiring a professional market research firm is cheaper than a lawyer. Start with it. But if you don't have the money, then any pro help is better than nothing. I am not a market researcher and I am just sharing my 2 cents and what I have seen.
Maybe because market research doesn't need a special license/degree like lawyers need or maybe because demand research looks easy to newbie from a distance, people think they can do it themselves. Most can't, and it's usually hubris to think you can or survivorship bias from startups that pulled it off. It will cost you in the vast majority of cases. There's always exceptions. Come visit NYC or Los Angeles and see the 10 million struggling arrogant writers who thought they could just write a successful movie script or book right away and didn't realize that professional experienced writers have skills they do not. Look into the "flop rate" of new products from companies that hire a professional market researcher compared to startup failure rates and it's clear that incorrect or lack of research is often a major problem. Good luck and happy new year.