The issue is that engineering and design converge insofar as measurable, quantitative data is available for a thing. Good UX is created by good instrumentation

The issue is that engineering and design converge insofar as measurable, quantitative data is available for a thing. Good UX is created by good instrumentation that allows for rapid testing and analysis of the way people use your interface as well as an unbiased knowledge of the history of UX. It's not exceptionally likely that a random "designer" will have or understand either of these things, and they're worthless if they don't. What's left for the people who call themselves "designers" is really just fashion, and it changes every few years, like all fashions. Clarke's Third Law, that good technology is indistinguishable from magic, is apropos in almost any discussion that touches on the osmosis between technical staff and laymen. The laypeople have seen Apple's meteoric rise and heard it attributed to "design", so they think they need a "designer". But Apple didn't get where they are just by hiring random designers. They got where they are by building an entire system that was centered around the vociferous pursuit of a few simple principles. Apple is Apple because they've inextricably ingrained these principles into the corporate DNA. Apple is Apple because they know that "vision" is only a minor part in good industrial design, and because everyone in the company is committed to developing products that exceed expectations along all axes, through art, code, analytics, and other major disciplines. Laypeople see Apple's attitude and success and think they just need to hire another plucky, divisive guy with an artsy feel to replicate it. They don't understand the work. To them, it's all magic, and anyone with a convincing robe and wizard hat is equally competent.