So you can make KDE the default but you’re going to be forced to ship a smattering of gnome/gtk apps anyway with different ui/ux and looks.
On the other hand, you can easily ship a GNOME desktop without even shipping qt libraries at all.
Even GIMP, the one GTK app I would never expect to be surpassed by a KDE app, is being outdone by Krita these days.
As I wrote above, more than a few large applications have switched away from GTK to Qt including Wireshark, Openshot, and now Audacity. How many large apps have switched the other way?
Then there are the "quality" apps that have always been on the Qt / KDE side of the fence: Kdenlive, FreeCAD, Krita, Scribus, qBittorrent, Qt Creator, Dolphin... And that's free software. It is a slam dunk for Qt on the commercial side.
My only dependents of GTK are Qalculate, Chromium and Firefox. I do not use the GTK version of Qalculate (but the Arch package includes it anyway) and I would never count modern web browsers as having a significant dependency on any UI toolkit. Am I missing out on a high quality Linux desktop experience?