If you compare KDE applications to their GNOME counterparts -- for instance, in music players, Amarok to Rhythmbox, or in DVD burners, K3B to Brasero -- you soon notice that KDE developers cram everything into the interface, while GNOME developers focus on the most common functionality.
KDE's kitchen-sink approach creates problems with organization. For instance, for several releases, the Systems Setting window had an advanced tab that was a dumping ground for utilities that didn't fit into any of the existing categories.
However, this approach also means that KDE developers are less likely to make assumptions about how users are likely to navigate the interface. They put everything in, and let users figure out how to work with them.
KDE is famous for its customization options. In fact, one of the main complaints about KDE 4.0 was that it lacked the array of options that KDE 3.5 had – largely because it was meant as a developer's release. But subsequent releases soon restored the level of customization that users expected, and the complaints soon died.
Moreover, while GNOME and Unity were reducing the amount of possible customization by eliminating or de-emphasizing panel applets and desktop application launchers, the KDE 4 series not only kept both, but encouraged their growth. KDE adds swappable icon sets and openly encourages panel applets (or widgets, as it calls them), especially for social media applications.
The same thing happened with file managers. When Dolphin became the default file manager, Konqueror was supposed to be the official browser. However, Konqueror lost none of its features, and can still be used for file management.
You might say that where GNOME and Unity bring order to the desktop by restricting customization, KDE embraced the chaos of conflicting needs and offered something to everyone.
Recently, GNOME has started emphasizing extensions. Similarly, Unity has encouraged innovations in lenses, the filters for the menu.
However, for every place where GNOME and Unity provide new ways to customize, KDE seems to offer two or three. Activities, desktop widgets, special effects, desktop setups, hot spots on screen edges – all these have been emphasized in KDE, providing more specialization than ever before.
The KDE 4 series opens up new possibilities to users. But it has also been careful not to force users to work with any of the new features. Despite all the emphasis on Activities, users can ignore them in favor of virtual workspaces, and work with a desktop whose appearance differs only slightly from what was available in KDE 3.5.
In much the same way, users who dislike the default menu can revert to the classic menu, and System Settings can be toggled from a window of icons to the traditional tree view.
Nor is there any discussion of phasing out such backward compatibility. KDE's default configuration amounts to a suggestion of which features to use, but does not compel users to accept the suggestion.