Actually, the only apps shown are system settings and the update manager. Hence, I am somewhat confused what you are basing your (strongly worded) criticism on.
My favorite design these days is an extremely minimal UI. A tiling window manager (StumpWM), Emacs, a terminal (xterm) and a web browser (Firefox). It's very efficient, and solves the design issue by having almost no design at all.
It can actually look really nice. See e.g. a some images from a random user with a similar setup: https://lepisma.github.io/wiki/misc/desktop.html
StumpWM is essentially Ratpoison reimplemented in Common Lisp. It's really good and stable, plus it resembles Emacs a lot. There's even a winner-mode.
There's not much to say except that you can tweak it till infinity and extend it in CL. But for me most defaults are pretty good already.
Some core devs are employed or have been employed by companies such as Novell, Nokia and Blue Systems.
It's possible to make a user interface that's both functional and well-designed. Indeed, good UI design improves functionality by making it more accessible and understandable. Things like consistency of elements and appropriate use of whitespace help to avoid mistakes and confusion.
I have to agree with the parent – it's also surprising to me how often otherwise excellent open-source projects are let down by poor user interface design. A large part of this is probably down to the more technical nature of the teams building them, who are probably the group for which design matters least. But I see this a lot in things like internal admin tools too – developers can quite often develop UIs that are so bad they actually become dangerous, and I wonder if some kind of "useful design skills for software developers" might be a worthwhile thing to work on.
If all i see when i look at the screen is a huge big gray panel, then it means nothing. There’s no important content, there’s just a background color taking up the space for no reason. If the fonts look tiny, it means they’re not important. If the colors are bland, it means nothing is especially requiring my attention.
Colors, font and layout are of the utmost importance when designning a ui because they convey meaning. Which is what a GUI is all about ( otherwise just use a terminal).
If all you see is a big gray panel, there's something seriously wrong indeed, because a panel without any content is useless. But that is not the case here.
> There’s no important content, there’s just a background color taking up the space for no reason.
The background color does not need a particular reason to "take up space". It is there when nothing else has a reason to be there. That's how a background works.
> If the fonts look tiny, it means they’re not important.
If the fonts look tiny, it means they're consistent with fonts elsewhere, including places where space is at more of a premium than in the installer.
> If the colors are bland, it means nothing is especially requiring my attention.
In the screenshots, nothing especially requires your attention. There are no warnings, errors, etc...
Of course something does requires my attention. There is content, and content has structure and different levels of importance. A screen in an installer is a step. A step has title, a domain, which probably would be nice to write somewhere. Then there probably are other steps i’ve performed, and other steps to come. Visual queues showing where i am in the navigation would be welcome. If the background is the thing taking up the most space, then it means the screen either has no reason to be fullscreen, or that the input doesn’t justify taking a whole step, ... etc
Those are the kinds of questions that you should ask yourself when you see a screen like that. Just based on visual layout and style.
Of course something requires your attention, the content of the screen. But if you highlight everything, you highlight nothing.
> A step has title, a domain, which probably would be nice to write somewhere.
It is.
> Then there probably are other steps i’ve performed, and other steps to come. Visual queues showing where i am in the navigation would be welcome.
They're on the left. I'm seriously wondering whether you even looked at the screenshots.
> If the background is the thing taking up the most space, then it means the screen either has no reason to be fullscreen, or that the input doesn’t justify taking a whole step, ... etc
If the background is the thing taking up the most space, it means that your screen is unnecessarily large for the task. That's unavoidable and not a problem to begin with. You can't just put multiple inputs in one "step", else you'd have a step with no coherent topic like Installation type+timezone.
In case someone reading this happen to be involved with the design of kde screens, i would suggest reading this kind of design 101 articles : https://www.canva.com/learn/visual-hierarchy/
Which is exactly the case in these screenshots. It is an installer step. The only "important" part is the next button at the bottom and it is full screen because it is an installer, hence lots of blank space (or slideshow distractions in other installers).