first of all, what do you mean by 'blindly following every Qt release'? We use it, how can you not 'blindly follow' a dependency?
second, KDE does far more than plasma desktop, heck, for the plasma team the desktop is just one formfactor they support. Calligra, digikam, amarok, Kontact and the numerous tools from dolphin and kdevelop to konversation and the hex editor (name i forgot), those all are done under the KDE umbrella.
then there is the work on frameworks 5 where KDE plans on becoming a prominent supplier of additional Qt functionally (and continue to integrate much other code in Qt proper, we are a leading contributor to Qt).
I really do not get what it is you are trying to say.