I wanted a nice qt theme to use on Scribus since Arc Dark doesn't work on there. When I tried to install it, pacman said this will install 50 packages. 300 Mb in total.
Why does a theme need packages such as Kauth and Kwallet?
I'd check that you're actually installing the most appropriate package. For instance on Ubuntu there's kid3 which is a MP3 tag application that will pull in the entire k desktop environment. Or you can install kid3-qt which packages its own version of those dependencies and doesn't pull an entire desktop environment in if you're using a non-kde environment.