I'm not sure if you realize, but this isn't intended as a "real OS" for practical use.
It's intended for use inside of computer games; whether for simulation of using computers inside the game-world, or for games where the framing device is a (simulated) desktop interface.
In which case, the "limited real world use" is hardly a flaw!
1. This is more of a design study that anything else, having unity provide your os shell is ridiculous.
2. You shouldn't consider your own needs the standard. I for myself would be very happy with
- A music player that doesn't integrate with user hostile, walled garden drm garbage
- Ditto for messaging
- Just using your own file sync for documents and pictures
Also, well, notes without filesystem access feels really useless, we can agree on that one.
- Music player without connection to the real world (spotify/youtube)
- Notes app without connection to the real world (the file system/other platforms)
- Messages app without connection to the real world (sms / messenger / whatsapp / etc etc)
- Photos app without connection to the real world (some kind of cloud synced file system)
- Notifications ... I really still have not found a use for them, except for IM on my phone
Stop bundling these things :( It looks nice, but the real world use is so limited. Focus on really enabling other stuff instead