The linked talk is full of half truths and misinformation by omission and already was when I first watched it in 2013. Most significantly the speaker conflates the X protocol and Xlib which nobody was using to write new software even back then. He says that gedit performs lots of blocking calls during startup. That's a problem of Xlib. With XCB you can perform all of these calls in parallel. He says that referring to an object that doesn't exist causes your program to abort by default. That's a problem of Xlib. With XCB, this simply returns an error that you can handle like you would do with any other API. He gets called out for this by one of the attendees but brushes it away with "but it's really hard to do". It's actually not.
I'm not going to go over the whole video since it was primarily made for entertainment and therefore any point can be defended by "he was exaggerating for comedic effect". Invoking this video is akin to invoking late night tv hosts when talking about politics.
And then of course he also has some valid points which are unfortunately diminished because the uninformed watcher will not be able to distinguish them for the invalid points.
I'm not going to go over the whole video since it was primarily made for entertainment and therefore any point can be defended by "he was exaggerating for comedic effect". Invoking this video is akin to invoking late night tv hosts when talking about politics.
And then of course he also has some valid points which are unfortunately diminished because the uninformed watcher will not be able to distinguish them for the invalid points.