At some point, I started calling myself "service designer" instead, because UX as a concept was fairly easily appropriated by visual designers (I guess what you call "UI designers") to mean "appearance."
Otherwise, what term do you use to mean that you're working to improve the experience of using a service across all interaction points it offers? I.e., across boundaries of particular screens, particular systems, particular company functions, or even particular companies in a few cases.
But I'd like to point out that it sounds like that, even while criticizing the wasteful focus on "look and feel," the look and feel seems to be exactly what bothers you, not the functionality behind it. If only functional changes mattered, we wouldn't register either way if they decided change the visuals of the system. You wouldn't need skins if the impact of it were immaterial to you.
It ends up that visuals are functional as well, and there's no hard line to draw between aesthetics and functionality. If I were to draw up a system that has great information architecture, navigation/findability, affordances, and the rest of it, but used terrible contrasts and font-weight: 100 everywhere, I would still have failed at making it usable.
I do agree that many designers seem to have some kind of pornographic relationship to UI, where they revel in it for its own sake. Personally, I consider UI to be cartilage: there should be as little as possible of it (but not less), and it should perform its function and stay out of the way as much as possible.
What "be as little as possible of it" and "staying out of the way" means is very contextual to service itself and the people using the service, which is why it is hard to establish a universally objective notion of what this means. It always ends up being an exploration to balance a vast set of variables.
Maybe Apple is completely right in making macOS more iOS-like, since familiarity is one way of staying out of the way, and they seem to want to focus on people who own an iDevice, but no Mac. But their current take on it has me worried that they've lost interest in accessibility (in all meanings of the word) as a design goal.
1) Why hide them? It is like hiding the steering wheel in the car and popping it out when you need it.
2) Why not make them discoverable?
3) Why can't we give a little bit of real-estate to the most important interaction - to unmute yourself before speaking - a permanent place in the UI by sacrificing sleekness a little bit?
This is not just aesthetics, far from it. There is so much horrible UI/UX/Service/Whatever-you-wanna-call-it in the world. It is filled with it.
I could write a 10 page article about Twitter's UI/UX. It is full of obvious improvements like this. It doesn't take an expert to notice these and they're not off for a debate - there is no subtlety or subjectiveness here.
People like yourself are rare and not that common. Most UI/UX folks are all about following design trends, aesthetic sensibilities and injecting personal taste into products as if it's some kind of a creative extravaganza.
Today we're getting new buttons, some other day we'll see the rise of some new technology and will think "yeah, that's the obvious thing to do", quickly forgetting all the other ones that didn't succeed, but were created through the exact same process of random exploration.
With the switch to a new UI paradigm (multi-touch) we lost discoverability, predictability through standard behaviour, shortcuts etc... why were UI designers not able to come up with innovations that improve the state of the art? Instead, touch UIs peaked with the first iPhone and since then became worse because more features were added without (I assume) serious usability research.
Instead of attempting to solve the actual problems that need solving, UI designers have retreated into their cozy corner of changing some completely unimportant surface details every couple of months, that's just an illusion of innovation. Smoke and mirrors.
I agree with you: the solution should be to allow users to not only theme their UIs, but to even modify them as they see fit. Consider GIMP for example. While some people like it's interface, other people complain that it's un-intuitive and not like Photoshop. Well, what if GIMP's functionality was separated from its interface, and there were two modifiable files that GIMP use: one that describes the UI elements (kind of like HTML: e.g., buttons, views, menu items), and another one that describes how those UI elements are displayed (kind of like CSS). Imagine if users could modify these HTML and CSS files to create different GIMP interfaces based on their liking. Imagine if the GIMP user community shared UI configuration files amongst each other. Users will have a lot more flexibility regarding how they want to use their software tools. This will also be a tremendous boon for people with accessibility needs.
This is not just talk; I'm actually currently in the design phase of a side project where I'm building such a UI toolkit for the X Window System in Common Lisp as part of a larger goal that I have of building a OpenDoc-style (https://www.youtube.com/watch?v=oFJdjk2rq4E) component-based desktop that leverages the powerful Common Lisp Object System. The UI toolkit that I'm planning to build will define UIs using three S-expression configuration files: a content definition file, a style definition file, and a localization file.
It would be fine if there would be an opt-out (let me install my own skins like I can do on pretty much every Linux desktop, and even on older Windows versions). Let me decide how ugly or pretty I want my computing environment to be.
UI/UX designers (I'm using the term interchangeably, because hell if I know what actually separates a UX designer from a UI designer) should focus on functional improvements, not on superficial fluff like colors and fonts, or whether a button is flat or looks 3D. Stuff like this should entirely be under the control of the user.
Oh, and the Hamburger Menu is not a functional improvement.