So backing up my save will require an Nintendo Online subscription?
Sony lets you back up your PS4 saves to USB drive, and they haven't been hacked like Nintendo.
Indeed. There is no sane reason not to allow backing up saves to USB. No idea why Nintendo didn't listen to any of the criticisms regarding Wii U's saves which were console-locked as well.
Console locked saves are terrible, and there is no excuse in this day and age.