[0] https://github.com/grassmunk/Chicago95 [1] https://garudalinux.org/editions (screenshots don't do it justice)
Once they finish sucking donations and other forms of financial support they'll probably announce it's time to "sunset" Gnome/gtk because it sadly didn't met unspecified expectations of unspecified group of people.
Gnome team, what they did and what they still want to do, their attitude towards users - especially those who dare to criticize them is THE result of polluting FOSS with corporate style of software development.
Theming and customization of Linux is half-dead because of what happens at Gnome.
To make my biases clear: I'm a software developer that uses Gnome daily, and is developing a GTK/Adwaita app. I used to rice a lot back in the i3 days, but I don't particularly care about that nowadays, and stick to the defaults when I can. For my purposes, GNOME and Adwaita is perfect since it's very opinionated by default, and you can make good looking apps with minimal effort. Since all Adwaita apps are supposed to look similar and follow the same HIG, most of my desktop apps have the same look - but more importantly, the developers of the apps can also be confident that their apps look correct on my desktop. This is something that developers in the GTK space generally want, and for good reason[0].
One argument is that you as a user of the desktop should be able to have the final say on how your apps look, which is a totally valid take! And there are DEs, WMs, and apps which give you this freedom like Hyprland. But this doesn't guarantee that those apps will look good, or look consistent with each other, or even act consistently across apps. On the other hand, I as an app developer want to guarantee that my app looks good on your desktop, and the easiest way to achieve that is to target a single desktop environment, rather than an infinite combination of possibly-similar-but-maybe-completely-different desktops. Every preference has a cost[1][2], and when you take this philosophy beyond just preferences and expand it to color schemes, padding, margin, iconography, typography, it becomes unmanageable.
This isn't to say that GNOME is perfect, and I disagree with the project on some fundamental technical things like not supporting xdg-layer-shell[3], and refusing to accommodate server-side decorations for apps which don't want to render decorations themselves. (On the cultural side I can't comment, since I have no experience with that.) But in my opinion, this is the project that can deliver a usable and consistent Linux desktop to the average person the most effectively.
[0]: https://stopthemingmy.app/
[1]: https://blogs.gnome.org/tbernard/2021/07/13/community-power-...
[2]: https://ometer.com/preferences.html
[3]: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/1141
When your app doesn't follow how my desktop looks it doesn't look good on my desktop. And unsurprisingly most modern Gtk3 and especially Gtk4 apps do not look good on my desktop.
What you actually mean here is that you want to guarantee that your app looks good on your desktop, not mine.
The counter argument to that is "so let the user theme the app, to suit their own desktop", which would be a decent solution, but:
1. My vision for my app might conflict with your vision for your desktop. Maybe I want this button to be a light blue because it meshes well with some other elements in the app, but you want it to be a darker blue because it fits with your desktop's color scheme. What happens then?
2. This still doesn't guarantee that the app will look good. If you theme my app's home page, but don't theme the rest of the pages, then sure it'll look good at the home page - but as soon as you start using it, the look will fall apart. Or, what if I push an update to my app which adds a new page with a new kind of UI element? Do you really want to be maintaining your desktop theme for every single app you have?
3. This adds a burden on me as the developer to make parts customizable. This is the least convincing argument in this list IMO, since if there was better tooling and infrastructure for theming in GTK this wouldn't be a problem - but there isn't, so it is still a problem.
As a practical example, my app makes use of a WebViewGTK to display some info. I inject some custom CSS into this web view to make it look like Adwaita. This touches on points 2 and 3:
2. The webview has some UI widgets which aren't present in the rest of GTK, like a sticky header bar. You would have to manually maintain a stylesheet for this single element.
3. I now need to write a way to let users theme the custom CSS inside the webview, rather than just the CSS of the GTK widgets themselves. (I have already written this, but it's still a maintenance burden.)
The user trying to make your app match their desktop should 'win'. Your responsibility is to ship out an app and make sure it works in the way you want it to work.
If the people need to do more work to make it look good on their desktop (as I likely would running awesoemwm), that shouldn't be prevented, but it also need not be encouraged. It should at the least though be facilitated, certainly to a better extent than it is.