Native look and Feel
Back in 2007 you could write Java so the GUI matched the native desktop. Any arbitrary Linux desktop, Windows Aero Vista or XP toned down to look like win9x/Win2K. It just worked. The ONE program distributed.
Maybe a little slow for some things, but it was a 1.8 GHz Mobile P4 I was using.
Since the advent of WPF (never finished), Vista, the pointless vb.net (c# was far better, anyone going from VB 6 was better to use C# for .net than VB.net) and .net has been a mess. UWP or whatever it's called this week was a better idea for PDAs & Phones than WinCE, was. But just as putting Win9x interface on a 320 x 240 device was brain dead, so was EVER putting mobile interface on Desktop Windows.
There are some good ideas in WPF and .net originally. They should have been in a new separate OS.
You need a different GUI for phones, big tablets (Android still bad on that), TVs/Setboxes and notebook/laptop/desktop. Android and iOS are optimised for smaller screens, no real keyboard, no mouse and consumption. Android TV is designed for streaming, games and desktop screens, abysmal for Satellite & Terrestrial broadcast or normal living rooms.
Desktop GUIs (Risc OS, Solaris, Linux Desktop Managers, Win3.x, NT/Vista/XP, Mac OS, Beos, Gem) use a keyboard and mouse. The Xerox WIMP concept has never been bettered and MS peak implementation was Win9x, NT4.0 to XP & Server 2003.
MS has lost the plot. So has Google with Android, but for completely different reasons and issues.