That's not entirely fair. That's still a pretty recent version - if you purchase from Amazon or NewEgg you have a good bet of getting it even on an x14 model, and certainly will get that or older on any other model - and there's no "Automatic Update" mechanism on Synology systems. Plus they're essentially storage appliances; users aren't expected to log into and manage them frequently. And the feature that seems to put people at risk is a selling point of the device.
I'm not bashing Synology; I have two Syns running in my system (both current, both firewalled, neither has the rumored susceptible port open, neither infected.) But you're not spending enough time around regular people if you think people expect to be logging into the admin screen of their external hard drive - or their fridge, toaster oven or coffee maker - frequently to check for updates.