Earlier quoted context omitted.
Theming was HUGE in Linux back in 2005-2010, consistency was paramount, adherence to toolkit was extremely important just like Apple claimed. For Apple it was about delivering a consistent branded experience, for the GNOME and KDE communities it was about being able to consistently customize the experience. In Windows? Always a free-for-all of such heavy customization on the side of the third-party applications that…
I agree that theming was much more consistent a decade ago in linux-land. GTK2 + QT with GTK2-style would get you an almost seamless experience. The "dark or light" theme we have today is an absolute joke by comparison. Many Gtk-engines were also much faster in terms of pure rendering speed. Another issue as mentioned is that per-control CSS skinning breaks easily with custom themes. Instead of using system colors de…
Ironically, you used to be able to use system colors via CSS. Like it usually happens on the web, that feature was also removed because of security reasons - apparently it made it easier for scammers to render fake system popups.