The “do one thing and do it well ethos” is a UNIX academic philosophy, specifically around command line tools. Most software neither write code like that nor necessarily ascribe to such a philosophy.

I can both hate the ideology and accept the software as having utility for me (not that I think I’ve used any of it, but in principle I have no problem with people being fascinated by TempleOS even though I am against a lot of the things the author has stated he stands for).