There is only so far an operating system can go, Windows and Mac OS X reached that peak moons ago - now they just add eye-candy.
Are you suggesting Windoze and MacOS are perfect? Far from it, in fact they still lag behind OS3.9. The stability, backwards compatibility, GUI, API, speed, and other aspects of Windows are inferior to OS3.9. Eg. they still don't ever have the scrollbar arrows located together, we have had that feature for nearly 20 years...The "improvements" being made to Windoze are mostly in the area of Digital Restrictions Management and such...I'll give such "improvements" a miss. The last time any worthwhile improvements were made to Windoze was the improvements between Win98FE and Win98SE, since then it's all been downhill.