A bridge supporting a weight load of X in wind/water conditions Y is a testable thing. A UI that is "easy to use", "intuitive", "has the things you use most fr

A bridge supporting a weight load of X in wind/water conditions Y is a testable thing. A UI that is "easy to use", "intuitive", "has the things you use most front & center", etc, are all soft subjective terms. Even when you run stats over a population to try to find generic mediums, those overall expectations will change over time as well.