To be fair, marketing and product strategy by necessity involves lots of guessing. Ideally those guesses are turned into testable hypotheses, tested, and the results used to make better next guesses.

Product research and development, even in IT, is often the same but using different data and metrics. There's no one right way that's readily apparent to build a finished project. We build mock-ups, testable units, unit tests, integration tests, and end-user quality tests. We reuse what works and throw other things away.

Anyone afraid to guess and test is just going to make clones of other products. Anyone who doesn't test is just guessing, which is less successful but may work if you're really good at guessing and really lucky.