So we just don't build GUI applications unless we understand all of the nuances of layout, text rendering, graphics programming, etc sufficient to implement it ourselves (and without the bugs that even domain experts have introduced but which have been found and fixed over time in libraries)? Or maybe we just say "fuck users who speak languages that aren't easily expressed in ASCII"?

There's a reason libraries exist. It's not like they were the default state of computing and no one has tried to write applications without them. On the contrary, we tried to build applications by writing everything ourselves, but that doesn't survive encounters with the real world. And "well if you can't do it yourself, you don't need it" (which may or may not be your argument, I genuinely can't tell) is just technologically regressive ideology.