If you want major security improvements, you want incompatibility
In your shop, when you upgrade security by changing the code in a program that has a version number, do you not increment the version number?
Most of MS's recent versions, security is what they're about. You change the release and version numbers as you make coding security updates.
And this is especially important for major security updates because major security updates almost always introduce some degree of incompatibility with poorly written programs.
Many poorly written programs, and even some well written programs, depend on OS features that violate security.
It isn't just OS X, Windows, Linux, Apache, etc. that have this issue. The internet architecture itself is incompatible with security and to become anywhere near secure against non-state actors would require such massive architectural changes that the new protocols and new code (including most firmware and software) would be incompatible with the old.
And for those others in sales and manufacturing, the ones who want the OS to have some wild new feature to sell their products:
1. An OS isn't supposed to sell products.
2. An OS is supposed to run the products that do the selling.
Desktops, lap tops, smart phones, tablets, their sales are not in the doldrums because of Windows.
Their sales are in the doldrums because of the lack of new hardware that can do something useful that the old hardware can't.
Blame Windows 7? If there was something that for most people and most companies was better that is what people would be running. I mean, Windows is cheap for OEMs, but Linux is free.
The only reason Linux hasn't wiped out Windows is it isn't as good for most customers.
And OS X, why don't governments and banks all run it? Because it is less secure against custom targeted attacks than Windows 7.
The thing that is wrong with Windows and MS isn't so much the products (although no software is perfect), it is the marketing, the PR and the management of expectations.
In those 3 things MS lags far far far behind Apple and even Linux.