I know quite a few Linux users, and not all of them are computer nerds (and none of them use Arch or are part of some small niche group). I'd say about 1/3 of them use Gnome, 1/3 use KDE, and 1/3 use something other than those two.
In general, it seems that those who are used to Windows get along better with KDE.
> KDE should stop assisting with fragmenting Linux
Having a selection of DEs to choose from is not "fragmenting Linux". It's a rather large strength of Linux to be able to select the DE that works best for you. I wish that were possible with Windows!
The fragment part comes from KDE nor GNOME coming close to the efficiency of DWM and Windows Explorer.
DWM and Explorer have low-latency, good hardware-acceleration, and power efficiency down to a T. GNOME 44 isn't on-par. I haven't heard anyone ever compliment KDE in these regards recently and back when I last tried it when Plasma 5 was relatively new it also wasn't up-to-par.
More work should go towards making these GUI toolkits run as efficiently as possible, instead of re-inventing the wheel slowly while macOS and Windows continue going strong.
The only way to make Linux DEs (at least on X11 -- I've never tried Wayland) as smooth as Windows 10's DE, I've found, is to disable composition. And KDE is the only DE I know of that lets you disable composition (yet another reason it's awesome). ;p
You lose transparency and animations, but the smoooooothness is amazing (and it even extends to games)!
I don't recall how smooth Windows 7 or Vista felt, but my conspiracy theory is that Windows lost all that Aero transparency IN ORDER to be so smooth (but that's probably apocryphal).
Nevertheless, Windows's DE and platform limitations are still horrible compared to Linux with KDE. :D As for Mac, that's tantamount to GNOME, so to me it's not worth considering as a contending GUI.
In general, it seems that those who are used to Windows get along better with KDE.
> KDE should stop assisting with fragmenting Linux
Having a selection of DEs to choose from is not "fragmenting Linux". It's a rather large strength of Linux to be able to select the DE that works best for you. I wish that were possible with Windows!