No, it's not mostly a Gnome problem. The default KDE theme, Breeze, is equally tablet-quality, and unless you want to fiddle with old QtCurve (which is nowhere

No, it's not mostly a Gnome problem. The default KDE theme, Breeze, is equally tablet-quality, and unless you want to fiddle with old QtCurve (which is nowhere near as space-efficient as macOS anyway) you're largely stuck with Qt's Fusion, which is itself barely tolerable. As for Gnome applications, it's not a Gnome problem, it's a GTK problem, that affects all GTK applications, regardless of what DE they run under, and all GTK-based DEs, like XFCE.