Windows is surprisingly resistant in the recent versions. The problem is that it is a complex piece of software with many parts, and no software is perfect.
Microsoft is the dominant player in the corporate workstation world, so it makes sense to target their platform for corporate and state espionage, and to zombify them for various other purposes that need a fleet of drone computers to perform.
This means that Windows has a large attack surface on both fronts, so it is aggressively being pummeled with attacks.
It is impossible to make the OS completely hackproof (due to issues related to the halting problem), which is why viruses are still a thing. They are getting more and more sophisticated as Microsoft makes it harder to do virus-like-things in their OS.
(The nastiest ones use the OS's own security model against the user. Nasty stuff there.)
Asking for perfect virus protection is like asking for perfect birth control. It does not exist, and the "best" solution is abstinence. (In this case, Not running every EXE you find on the internet.) As they say in the medical profession, "an ounce of prevention is worth a pound of cure." Same way in preventing viral infections for PCs.
All wrapping each process inside a sandbox would do, is move the focus of the virus programmers to breaking the sandbox, and getting control of the hypervisor. Trust me, the motivation would be there (both mental and monetary), and it would eventually happen. Sandboxing isnt a silver bullet.
The problem I have with modern windows is not what is under the hood-- it's what they are doing with the userspace. The UI is horrible! It's like Microsoft is taking every "popular" thing, and gluing it to the UI like a tawdry bauble. "let's stick twitter integration icons EVERYWHERE! Facebook too! You know what, let's display thumbnails of our news service's top story every time you click the start button!" and all that shit.
No. How about "I want to do my work now, go away." eh microsoft?
There's nothing wrong with providing the OPTION to have that level of deep hentai tentacle penetration with social networking if the user really wants that-- but it should not be a mainlined feature that is assumed to be on.
I dont have a problem with windows concerning what's under the hood. I have issues with how they are trying to engineer user experience and user consumption. They are trying to dictate. They confuse that with "Leading." It is NOT the same thing. It will continue to kill them until they learn their error.