Hi Markus,
No discourage at all :)
I see your point here but I think you are only partly right. IMHO I see other small applications in the repository too. In addition, WallpaperDownloader is already in AUR and available as a snap package in the Ubuntu Store, being daily used. Some of those users have complained because the truth is snap packages are still in an early stage, so there are some crucial aspects of the application (the automated changer for example) that doesn't work properly in some cases within an isolated environment as the snap package.
Because of this, and because I think the right of choice is very important in the Open Source world (I know there are scripts that can download wallpapers and applications like Variety that are already in the repos and are quite similar [although they have different features]) I decided to start packaging the application for Debian.