Microsoft operating systems are produced by a separate team of developers. Office, and other Microsoft software is all developed by separate teams, but obviously there has to be a constant cross-flow of information to ensure that everything works smoothly with everything else.
The problems out in the userbase invariably arise when people start running all kinds of third-party applications and tools, plus hundreds of different hardware devices. Beta testing programmes can iron out thousands of the incompatibility problems, but thousands more will come to light when you have the operating system installed in five million machines. That's only half the story - once you've found the problems you have to solve them, and that often requires a good deal of cooperation from hundreds of different software and hardware companies.
Like any other business, Microsoft exists to make a profit, and it will only continue to do so if it can sell software - millions and millions of units of it. It's very much in Microsoft's interests to have happy customers, and I know how hard the developers try to act on all the feedback they get. Unfortunately, if you ask 100 computer users what they would like in their ideal operating system you'll probably get about half the people in broad agreement - the other half all come up with slightly different answers, and that's what Microsoft has to address.
I'm sure that everyone who has worked with the company as long as I have would agree there has been a major change in the way the company interacts with its userbase over the past ten years or so. Time was when it was next to impossible to get a meaningful response from anyone about anything, let alone establish a dialogue, but that's changed. I can contact the Microsoft Press Office on more or less any subject and be guaranteed an answer from someone who speaks for the company within a day or so. I don't always get the answers I want, but at least I can ensure that my voice is heard.
Maybe one day we'll all have the ideal operating system, but I doubt it, any more than we'll all have the ideal car.