Interesting piece - reading it I found myself skimming, the point being made was being made repeatedly, albeit showing that as the author grew as a developer so did the complexity of the software they were using.

There was one thing that screamed in my head, though, whilst reading it, was, yes we can have a look at the library being used, read the code, and understand what its actually doing (this is one of the reasons I like Go so much, no matter who the upstream author is it's generally clear what they're doing [caveat: there are always going to be authors that obfuscate the f*ck out of code, no matter the language], the one thing, though, is systems like Netflix, hundreds of microservices running together in ways that people have NFI what it's all doing.

It just doesn't fit into one person's head anymore.

So, a single head can manage the data pathways for some subset of the system overall, and they might even get right down to the metal, the sheer size of the system means they only have a partial view, and abstractions (in the form of C4 diagrams) only show how complex the beast has become.