While I don't know about that Vista problem, it's not true that Microsoft doesn't innovate in the kernel. Windows 7 introduced the "MinWin" kernel refactoring which significantly reduced the OS footprint, see the 2009 talk & slides by Mark Russinovich:
Windows 7 and 8 both have lower system requirements than Vista while offering more features. That fact was widely advertised and acknowledged. Sure, not everything was improved, but it's not true that MS never fixes things for better performance. They simply have different business priorities, such as supporting tablets in Windows 8 rather than supporting 1000 Mbps.
The OP didn't say there's no innovation at all in Windows. He just said it's slower than in the Linux kernel, and as a consequence atm Windows lags behind Linux in performance-critical usage scenarios.
http://technet.microsoft.com/en-us/video/windows-7-and-windo...
http://download.microsoft.com/download/8/C/2/8C21BAFE-3432-4...
Changes in Windows 8 were smaller, but it did for example improve the efficiency of memory allocation:
http://blogs.msdn.com/b/b8/archive/2011/10/07/reducing-runti...
Windows 7 and 8 both have lower system requirements than Vista while offering more features. That fact was widely advertised and acknowledged. Sure, not everything was improved, but it's not true that MS never fixes things for better performance. They simply have different business priorities, such as supporting tablets in Windows 8 rather than supporting 1000 Mbps.