Doesn’t this quickly become untenable? Sure, you might be able to code some of your own tools, but what about the OS those tools run on? Hardware? Drivers?
This is kind of covered in that manifesto itself in that you only go down the road of making something yourself when the tools you use no longer match your use case.
A lot of tools will be fine or meet your goals, such as your OS. If your OS doesn't match your goals then you're left with the three options detailed. In the case of an OS, the "big" OS's probably meet most people's general computing needs. It's not uncommon to write a custom "OS" for embedded devices. Some people do feel like making their own OS and there are plenty of examples out there of them and that's perfectly fine.
Anything like this is also not written as law. Your text editor annoys you under these certain conditions? You don't have to rewrite it, fix it, or switch to another editor. If you're compelled to write a replacement, it shouldn't be stigmatized which rewriting existing software frequently is.
It _immediately_ becomes untenable, actually. It'll like telling people to "manufacture it yourself". That might be possible for a perfectly fit person living a Robinson Crusoe life in some remote region; otherwise it's just divorced from reality.
We are a social animal - "zoon politicon" in Plato's original Greek - and our activities are social. For better and for worse, we can't declare that not to be the case or claim that we want to just be "left alone".
A lot of tools will be fine or meet your goals, such as your OS. If your OS doesn't match your goals then you're left with the three options detailed. In the case of an OS, the "big" OS's probably meet most people's general computing needs. It's not uncommon to write a custom "OS" for embedded devices. Some people do feel like making their own OS and there are plenty of examples out there of them and that's perfectly fine.
Anything like this is also not written as law. Your text editor annoys you under these certain conditions? You don't have to rewrite it, fix it, or switch to another editor. If you're compelled to write a replacement, it shouldn't be stigmatized which rewriting existing software frequently is.