Every desktop environment is a hodgepodge of inconsistent UI design at this point. Windows has never been completely consistent; IIRC even Windows 95 had some settings dialogs that came along from Windows 3.1. Linux has GTK, Qt, and several toolkits aping aping them with various levels of success. MacOS comes closest to uniformity, until you start paying attention to title bars or run popular 3rd party applications on it.
On Linux (and, generally, under X), you at least have copycat skinning engines, so that you can have your Qt programs mostly copy the look of the current GTK theme, and vice versa.
Under Windows, no such thing existed and exists, unfortunately. One thing that I had hoped when installing Win 95 back in the day is that old binaries that use standard window-drawing functions will automatically upgrade to the new look and feel. Not all of them did, alas.
