Mostly by relying on the stable-because-they-are-outdated distros, e.g. Ubuntu/Linux Mint -- which is what non-technical people do anyway.
There is a barrier to entry, though -- you have to at least have enough skill to install an OS from a DVD. Maybe that helps...
Anyway, that has nothing to do with calibre, just linux in general. Maybe you shouldn't take Kovid's word as gospel truth on the generic topic of the Linux Desktop.
Especially as I suspect his rant was actually motivated by continuing frustration over the patch-happy nature of many distros, which is a separate point (and why it is recommended to install the version distributed from calibre's website).