KDE Plasma is great and actually seems to have inspired a bunch of Win11 approaches, so it is possible to get things looking good but there's definitely truth in the sentiment above: a huge chunk of OSS software looking terrible.
There's always the form vs function debate but it's a shame that more doesn't manage to have both form and function if the respective specialists could coordinate
Less polished in some areas too, though. It's slowly improving over time but for example fine UI/UX details like whitespace usage, control alignment/placement, and typography have always felt a bit… "off" in KDE as well in most software written with Qt, which I think probably boils down to Qt being more likely to be chosen by devs who are more technically inclined than design or UX inclined.
In my opinion GNOME and GTK apps generally get those details more "correct", though GNOME 3 and up goes way overboard on padding. Strip that padding down with a theme and its design is solid though, and Cinnamon, XFCE, and MATE get these right out of the box with no modifications necessary.
But that's why these "X has a better UI than Y" arguments are silly. I prefer KDE to any other DE because it worked (I now use MacOS and can't run other DEs) for me, and most people who prefer other DEs. That's OK. They all have different strengths and weaknesses (customization, resource usage, ability to run on certain OSes, high DPI support, etc).
i still use MacOS and windows from time to time, and i simply have to disagree. using MacOS has just as many WTF moments as i get with Gnome (and KDE too i think, but i haven't used that in a while) a windows just leaves me baffled every time i have to touch it. ( https://commadot.com/wtf-per-minute/ )
The one thing I think is great in Windows is the whatever the active apps bar at the bottom is (taskbar?). Hover, get thumbnails, etc. On mac, I find it kind of painful to juggle a few windows of the same application. Can say the same in Linux as well, some apps don't even show up at all, even though they're running in a window/viewport.
I genuinely like and dislike most OS UIs I've tried. They all have things that irk me. While windows settings has gotten more consistent, it's also all the more painful when you had gotten used to the "old way" of doing things and where to look. If MS executives could just get TF out of their own way on some of the stupidity and force-feeding.
Mac, just feels a bit dated at this point, but the touchpad integration across all apps is great. Not to mention the macbook touchpads being second to none in terms of usability.
Linux, I can shift to almost exactly what I want. There are rough edges and spots you cannot reach via UI, but it mostly works without issue. Been using Budgie as my DE for over a year, fairly customized and like it a lot.
Also, if you’re at the command-tab picker, the up arrow key will switch to windows of the currently selected app (and left/right arrows will change the currently selected app). The macOS command-tab switcher has a bunch of functionality built in.
discovery of hotkeys can be a challenge. despite having used gnome for years now i only recently learned that i can switch windows with alt-esc instead of alt-tab, which is much faster when you have multiple windows of the same app or want to switch back and forth between to windows. and i only found this while searching for an extension that would make switching windows easier.
There's always the form vs function debate but it's a shame that more doesn't manage to have both form and function if the respective specialists could coordinate