Your NAS is not critical. The plan if your NAS gets compromised is to say "dang" and wipe it and re-download all your movies or whatever. You can connect that to the internet.
Stuff like your town's water, transportation, and medical infrastructure and employee and student data are critical. Your car's drivetrain and safety features are critical. Your home's HVAC can be critical in certain times of year. These things should not be connected to the Internet.
Stuff like your town's water, transportation, and medical infrastructure and employee and student data are critical. Your car's drivetrain and safety features are critical. Your home's HVAC can be critical in certain times of year. These things should not be connected to the Internet.