The confidence that "it's just going to suck" really highlight out this is really ideological rant not a technical conversation. As such I don't really think there is much to talk about the video itself, there isn't any substance.

As for the underlying question terminal emulators do seem to be REALLY hard. I don't think this has to do with language/OS complexity as much as the complexity needed to be compatible with apps that expect the terminal to work a certain way rather than just being an easy way to display text on a screen.

Would be curious to hear from people that actually work on terminal on what is it that makes them more complicated than they look if any are reading this thread though.

Writing a terminal emulator is a pain in the ass. Thats all I'm going to say.

TL;DR: What is wrong with the world that software that prints text to the screen has/needs a special project by a megacorp to make it perform/operate acceptably.

But you could say the same thing of browsers.