Every decade since 1999 (the year of the Linux desktop—for me) I spend a few weeks trying out all the hot new shit in terms of desktop environments. I'll switch to Gnome for a few days, get disappointed at how much I miss from KDE, and then try one of the newer ones like Cosmic. Then I'll play with the latest versions of the classics (xfce) and marvel that they still make you configure everything in a single file or they still lack basic shit that normal people want like a clipboard manager.
All the actually useful or just plain really, really nice/handy stuff is built into KDE Plasma. I've been using so many of those features for so long, I can't fathom having to go back to a world without say, being able to navigate the filesystems on all my other PCs via ssh:// (and other KIO workers).
I remember when KDE 2.0 came out and it added support for kioslaves (now called KIO Workers) and it completely changed how I viewed desktops. That was in the year 2000. How is it that literally nothing else (not other FOSS desktops nor Windows or Macs) has implemented the same feature?
It's not just the file manager, either. I can access ssh:// (or any other KIO worker) from any file dialog! The closest thing is shared drives in Windows but even that isn't nearly as flexible or feature rich (or efficient, haha).
Then there's the clipboard manager (klipper), Activities, and a control panel that lets you customize everything to extreme degrees. It even supports fractional scaling and has supported that since forever. I remember when they introduced that feature over a decade ago and it still blows my mind to this day just how forward thinking the devs were.
Monitors since forever have had a different X DPI than the Y DPI. Yet only the KDE devs bothered to both query the monitor's DDC info to figure that out and set it correctly when the desktop starts.
There's other features that drive me nuts when I don't have them! For example, the ability to disable global shortcuts on specific windows. So if I've got a remote desktop open to my work I can send Super-. (Win-.) and that'll open the Windows emoji picker in the remote desktop instead of the KDE one (locally). And it will remember this setting for that application!
I can make any window I want stay above others temporarily to take notes, enter values into the calculator, or just turn any window into something like a HUD (you can control any window's transparency on the fly!).
It even supports window tiling! A feature most people aren't aware of. Like, if you're already running KDE, why bother with a tiling window manager? You've already got it (though the keyboard shortcuts to manage the tiling layout in real time are lacking).
TL;DR: KDE Plasma is the best desktop in existence across all platforms and this is easy to prove with empircal evidence.
Did you change the ink during this process? I've found things inside printers before.