I would disagree with that. Virtual desktops also offer something priceless: the ability to group applications semantically and reducing the friction in finding said applications (i.e. if I need my browser, I know it's always on desktop 2, I don't have to cycle or anything). I agree that having a multi-monitor is a great step in that direction, but it's not quite the same in my opinion.

Note that Microsoft has offered multiple virtual desktops in the past (in the form of what I think was called Power Toys), but never integrated that in their OS.