Writing your own OS/Browser/Editor/etc

Its like building your own home. It sure feels like you're in control but the effort wasted is not comparable with the little effect(low popularity, less use cases). People who dedicate their entire life to a software project as a hobby/work/noble cause are a different matter.
The idea of writing X because you don't like Y is just silly - you really want to dedicate all your life to maintaining and improving a piece of software, just because you're incapable of dealing with flaws in existing software?

while I agree it's usually not worth spending your life making something like an OS (unless your hobby kernel catches on like Linux, which it probably won't), I don't think there's anything bad about doing it for a few months. it sounds like a great way to learn both low-level programming and useful algorithms and data structures. same for making a compiler (or even your own programming language).