If you accept that cat and grep where the right tools and still are the right tools then you can not say 'do just one thing well' has been rendered obsolete and so it is still applicable to some cases at the very least and you must show it's not applicable to pid 1 programs.

I am also arguing more for openrc which is a newer project that has notions of dependence's and such.

If I may show where I think 'do only one thing well' is violated and correctly so is emacs (at least in part), for by having emacs as what boils down to a constant text interface I can use generalized text editing, searching and deriving buffers all in one program not having to configure anything else, my editor is my console and I can use my editor tools in my console even the ones I make.

So where is it demonstrated that the coupling is a boon that out weights the cost.