Customers don't know what they want. There's plenty of good psychology research that shows that people are not able to accurately predict how they would behave in the future. So asking them 'Would you buy my product if it had these three features?' or 'How would you react if we changed our product this way?' is a waste of time. They don't know.
Training is such a vital part of preparation for a game you really do train to play. It tops up your ability like sharpening a carving knife. You can get away with not doing it for a while as long as you have reached a certain standard of fitness.