So the world consists of apps like Slack, and Photoshop, and Final Cut Pro and none of them are written in Qt or GTK or any of the other libraries you mention.

So the world consists of apps like Slack, and Photoshop, and Final Cut Pro and none of them are written in Qt or GTK or any of the other libraries you mention. Any one of those applications has more installs than Debian on a desktop (this is an educated guesstimate).