Aren't a good number of viruses blocked by your router? The rest either rely on tricking you into running a program (updates can't stop that but reduce the damage it can do) or come from javascript garbage or browser exploits (less dependent on operating system flaws). although there is zero-click malware around; but if a malware is zero-click it probably also has tricks to bypass the latest updates.

If you close listening ports and don't port forward, it should be safe enough.that relies on you trusting that your router works properly and that the virus isnt already inside your LAN or has exploits targeting routers.