Force applications to use Adwaita Light

I am looking for a way to force all apps to use the light version of the Adwaita theme. As it is now, apps like Totem, Eye of Gnome and Photos use a black theme which sticks out in a very ugly way compared to my other apps.

I managed to use "GTK_THEME=Adwaita:Light totem" to do this when launching apps, so I know it's possible. But adding this to the .desktop files doesn't seem to work. I would like to have a permanent solution that makes this work even if I just open an image from my file manager or such. Is there any way to do this? Perhaps I could automatically add "GTK_THEME=Adwaita:Light" to all app launches in some way?