But a unix system has a module system: the filesystem and its folders. The fact that there are a number of "functions" that are in the same "default namespace" is just a convenience: if needed two binaries with the same name can coexist.

Also i will add that in fact the systen binaries are already split: at minimum /usr/bin and /usr/sbin (but also historically, /bin and /sbin although i think in recent linux system the last two are just symlinks to the formers, or the other way around)