Apple

To be honest a lot of features are still missing. So I would say there's definitely room for improvement.

1. Split screen

2. Better sound settings. Alarm power level is still attached to the ringer. Absurd.

3. WiFi share similar to hotspot

4. Since they allowed custom icons, widgets, etc we need be able to move them as we want

5. That's a personal and unpopular one, but I really like the idea of having fingerprint sensor in the lock button.

6. iPhone needs to manage its memory better. Currently, if you are in an app and downloading something, close the app ti check something, the download could go to kb or even stop. Your current session needs to be open so the phone dedicates ram to it. It's bad ..