One point even complains that there's adobe flash video tearing... so? Adobe dropped support for Linux, what the hell do you want Linux developers to do to fix that?
No high level, stable, sane (truly forward and backward compatible) and standardized API for developing GUI applications (like core Win32 API - most Windows 95 applications still run fine in Windows 8 - that's 18 years of binary compatibility). Both GTK and Qt (incompatible GTK versions 1, 2, 3 and incompatible Qt versions 2, 3, 4, 5 just for the last decade) don't strive to be backwards compatible.
The backwards compatibility is why Win32 is garbage and they had to make winforms for .NET.
I can point to almost anything related to software development and its flaws will almost be entirely with backwards compatibility, you'd think an area that just started existing in the past half-century would be fine with fast progress.