Unfortunately the triplet DE--GUI-Toolkit--Applications is often intertwined or at least evolves in the same manner.

For example, I don't want GTK-3, I only have GTK-2 installed. It could be all fine and dandy if, one after another, year after year, applications wouldn't give up their GTK-2 backend to only maintain/develop their GTK-3 one. The set of (up-to-date) applications I can run decreases, despite the fact that, as Alxlaz, I still run WindowMaker :-)

On Qt side, there are applications which requires an exact version of Qt (not only the main version Qt-3/4/5, but the point version), or require KDE, or require an exact version of KDE. If you want to install a new application, you have to go back in its history and find a version of the application that matches your installed library version. Or install another Qt version and hope it doesn't break other programs.

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A bit different, but many years after my last try, I tried to use Scribus. I quickly remembered why I had not really used it long the previous time: text input is still convoluted and not WYSIWYG, which is a bit annoying (understatement) for this kind of program where you precisely want to see how text flows. So I gave a try to the new branch (which BTW required a new version of Qt, if I am not mistaken), hoping that they finally did something about it after all those years this program exists. Alas! Apart from the underneath Qt version change, the visible changes were: icons are now flat and monochrome (i.e. you cannot recognise one from another), keyboard shortcuts have been slightly and viciously modified (what was F3 is now F4, stuff like that... but why, oh why? what is the freaking point of doing that?), and it crashed on me after 5 minutes.

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So basically, even if you'd just wish to have a few bugs fixed, and possibly a long-time missing feature finally added, by getting the new version that does this, you are forced to follow the crazy flow of adding or updating all libraries/toolkits/environments, because maintainers have decided it was way more interesting to rewrite their stuff for the umpteenth time with a different/new back-end (toolkit, environment), rather than polishing their existing, mostly fine for the job, code base.

It is exhausting, I am, too, really tired with that churn and constant breaking.

>For example, I don't want GTK-3, I only have GTK-2 installed. It could be all fine and dandy if, one after another, year after year, applications wouldn't give up their GTK-2 backend to only maintain/develop their GTK-3 one.

gtk2 is deprecated, so it makes sense that any actively-supported applications are moving to gtk3, which is still supported. By refusing to use gtk3, you're locking yourself out of not only newer applications that were only written for it, but older ones that have moved to it.

Why do you think an actively-maintained application should stick with a deprecated toolkit?

>On Qt side, there are applications which requires an exact version of Qt (not only the main version Qt-3/4/5, but the point version), or require KDE, or require an exact version of KDE.

In all my years, I've never seen this with an actively-maintained application. Of course, I generally stick with stuff that's available in my distro repo, so I never have any trouble.

Also note that with both gtk3 and Qt5, both these toolkits have been around for something like a decade now. Looking at Wikipedia, gtk3 3.0 came out exactly 9 years ago (10-02-2011), and Qt5 came out on 19-12-2012. Neither of these is at all new. I will grant you, though, that gtk3 is now already headed the way of the dodo, since they've announced gtk4. Personally, I'm not a fan of gtk and prefer Qt as it seems much more stable and better for GUI development anyway, and I don't see anything about Qt5 being phased out. Qt is also used a lot in embedded systems in industry, unlike gtk.

>the visible changes were: icons are now flat and monochrome (i.e. you cannot recognise one from another)

That's all the rage these days. I'm not a big fan either, but it's what most users want. This isn't a brand-new fad either; it's been going on for years now. I do wish I could try living in the alternate universe where UI design mostly stuck with way things were done in the mid-2000s.

I use Kubuntu LTS, sometimes I had to compile a program that was abandoned and I wanted to keep using it. In the last year though we get snap and flatpacks so in theory this could work in future unchanged(though you can't be 100% sure). About the icons, good developers use the system icons so installing a different icon pack compatible with GTK2 would solve the issue(not if the developer included his own icons). About OSX , I think they just dropped 32bit support so I suspect you would also hit issues where your old favorite application is broken,

I understand the frustration with tech , I also went for a short while to Windows10 then I went back to Kubuntu and not even dual booting anymore, the largest frustration I have at this moment is sometimes my video card crashes and I am not sure if is the NVIDIA driver fault or is an hardware issue and on top of it people would say "Why did you bought NVIDIA ?, AMD is better" but at that time I bought my card AMD drivers were shit and most Steam Linux games only supported NVIDIA.

I would also blame developers, the open source and proprietary software developers want to use latest and coolest thing, then sometimes they are forced by deprecation of old tool kits to change (at least sometimes GTK2 apps are ported to the better Qt toolkit)