Maybe the UX designer's job should include more statistics and analysis? It's not enough to draw mocks for engineers and do a usability test now and then.
Unfortunately, the hard truth of it is that most "UX people" are in environments where the post-implementation cycle is ignored. For as many companies out there that claim to embrace the "UX process," I'd say that well over 80% of them don't actually embrace it beyond feature release.
It's not that the UX guy knows it better than yourself, but he strives to be able understand it and then to state it more clearly, in an actionable manner. I don't know the call-center operator problems better than he does, but I was able to identify the pain-points and improvements more clearly. While the user will know the problem way better than I do, I can't expect him to systematize and conceive solutions, as well as ways of measuring them.
That's actually what most UX methods tend to to, nowadays. Instead of asking the users, the UX guy will observe (e.g. do job-shadowing).
At least, I've spoken to a few people who feel like that. And I've worked with quite a number of UX people who didn't really seem to have any skills I could easily discern as being useful (but definitely could produce reams of wireframes that made absolutely no sense whatsoever - I remember one hapless UXer who made 10 pages of wireframes describing how he wanted a file upload dialog to work before a developer gently informed him that said dialog was entirely governed by the OS and we would have no control over it).
There is always a balance between the two. There's room between the pain that is design without consideration of the information and the user, and information accessibility with no consideration for visual aesthetic.
Edward R. Tufte
App developers will create whatever they think might stick. Further, if there were not merit in simplicity, such apps wouldn't be successful.
You are claiming a universal inferiority. Deriving a universal principle from your own singular experience.
That inability to recognise the existence of other viewpoints, and other markets, is why you need a designer's empathy.
Ironically, one can also speak of UX-isation of design. I would define it as misguided thinking that the designer knows my problems better than myself. Take "you should take your umbrella" weather app. The information density is exactly 1 bit per screen which is abysmal. What about my jacket? Or what if I want to play badminton? Just give me the temperatures and wind info dammit.