Unfortunately, this is not an area that KDE is responsible for. KDE is a desktop environment. It's main concern is the desktop software and libraries. It doesn't make packages either and distributes source code only of KDE software. KDE leaves it up to the distribution or operating system to take care of resolving and installing the dependencies required to compile, install, or run KDE. As such, it is something for distributions to chew on. KDE itself is not a complete OS.
That said, there are some "alternatives". PC-BSD implements a packaging system similar to this I believe. There is also a project called klik2 which allows you to temporarily/arbitrarily run KDE software using a sort of image. Take note however, that even the klik developers do not recommend nor do they plan to make it a substitute for real package management.
Anyway, most modern Linux and BSD distributions today have very mature package management systems. Distributions such as Kubuntu, openSUSE, Debian, etc. all have package managers that are quite easy to use, without the user having to necessarily deal with dependencies. If your distros package management isn't doing it for you, might want to try out other distros, or help your distro in making things better.