I'm sure it's very nice but tying an audio player app, or a text editor, an rss reader, or any other such tool to one specific desktop environment is an unbearably stupid idea and makes me think that both Gnome and KDE have made a seriously wrong turn somewhere.
I was annoyed that Gnome didn't have a very basic "sound file player", everything polished wanted to be something more, like support for music libraries, etc. I downloaded a single wav file, I want to listen what's in it, there was no perfect app for that.
It’s not that bad imo, probably good UX wise. People using gnome have a specific mindset/expectation that usually does not apply to people using KDE (and reverse).
Most of the heavy lifting is done by lower level libs anyway. So the duplication is not as extreme. E.g Firefox doesn’t gel well with KDE by default. And thunderbird looks quite foreign.