Xubuntu window bar font not rendering properly with dark themes
"Ugly" is a relative term. The theme developpers may like that. Indeed, you may want to change your window theme. In XFCE, use Window Manager settings to set a different window theme (i.e., the look of (legacy) window decorations: title and border). That theme is independent from the theme used by the application.
Xfce uses two different themes for the window borders (window manager theme) and the window content (GTK theme). The first can be set using the Window Manager application, while the latter is set using the Appearance application.
The problem you are facing occurs in Xfce when you are using the default Greybird window manager theme with a dark GTK theme. The solution is pretty simple if you wish to use Greybird as your window manager theme:
- Open Window Manager.
- In the Style tab search for and select the Greybird-dark theme.
- Click Close to close the window.
- You may need to restart the open applications for the theme to apply.
Dark themes should now work correctly, with white-colored fonts in the window title bar.