The reason I put air quotes around "designer" was to convey the fact that I believe _good_ designers would base their decisions on logic discovered via some for

The reason I put air quotes around "designer" was to convey the fact that I believe _good_ designers would base their decisions on logic discovered via some form of the scientific method. Studying what makes user interfaces understandable, and why. Data doesn't need to be "track everything the user does and do A/B testing", it can come from many sources: user behavior studies done in the past, cognitive psychology, experience gained from mentors, etc. Would you make the same "they do it every day so they must be right" argument for engineers? Product managers? Stock brokers before data-driven trading? Doctors before the rise of modern medicine?