Windows 10 Criticism for not being Linux is unreasonable

The short answer is: No, it's generally not fair to criticize Windows 10 solely for being different from Linux, because "different" implies a value judgment that one way is correct and the other is wrong. And as you noted, they serve different purposes and user bases.

Criticizing Windows 10 for issues such as privacy concerns, update management, user interface choices, or system stability is valid because these are areas where users expect improvements. Recognizing that Windows and Linux are different doesn't mean you can't compare or critique aspects of Windows based on your needs or preferences.