Programs that we think of as being part of the OS, such as the included text editor, is a very different thing to something like Steam, imo.
Steam isn't preinstalled on your PC, it's not a core part of your desktop OS. You download Steam yourself, so you'd only do it once you already know what it is.
Third party apps kinda need unique names and branding like that to distinguish themselves.
A newbie won't know what "Kate" or "Okular" do. They might know what "Dolphin" does because it has a folder as the app icon (although users of screen readers won't see that). They will probably know what "Notepad" or "Text Editor" does, though.
Indeed. That's what I do on my Plasma system, it's a good option.
But a new user or someone who isn't technical won't see that, they don't go digging through settings in each app, they just use the defaults.
I guess a solid compromise would be to enable this by default, and anybody who doesn't like that short descriptor can disable it.
But IMO nothing will beat the no-nonsense straightforwardness of calling OS apps immediately intuitive names. This is something I believe Gnome gets right. Go onto their GitHub and their file manager is called Nautilus, but on your system it will default to being called "Files", because they know everyone will understand what "Files" is but a lot of people would ask "Wtf is Nautilus??", same goes for other apps, e.g. "Loupe" appearing as "Image Viewer".