The functionality is there, and so is the usability, but the design is highly lacking.
Let’s take Office 365 (July 2016) and LibreOffice for example.
Icons are lain out in categories and even sub-sections within these categories. The icons fit the pixel density of the screen and they are of relatively modern design.
This was the cleanest part of the interface. On Windows, LibreOffice has the convenience of the menus at the top but in Linux, they’re not so present, sometimes non-existent. The icons are bulgy and outdated. They’re of inconsistent design ideology. The icons are however just all in one place. It’s overwhelming to be honest.
With GNOME 3 and Unity, Linux is on its way to being beautiful, but something needs to be done to make Linux more HiDPI friendly. Linux needs to have a more consistent design ideology and developers need to work a little more on the polishing of their software.
However, it might not just be a Linux issue. It could just be in the world of Open-Source.