I think you missed the philosophical justification at the beginning of the series. This is Handmade Hero we're talking about where we build every system of the game with no help from libraries, frameworks, or engines. The whole point is to show people how it all works from soup to nuts.

Using libraries, even the STL in C++, would be cheating.

In the bigger picture of things these abstractions have costs. They're not free despite the C++ propaganda machine telling us otherwise. It's important to know what those costs are in order to make effective decisions about whether to include them in your project.

And finally the golden rule: if it looks right it is right. We're not here to write pretty, elegant code. Your pretty abstractions don't matter to the hardware. The target platform your system runs on is likely a highly-optimized piece of circuitry with real, physical constraints. Casey is the first programmer I've seen teaching people to keep the Intel manual handy and how to implement data-structures for cache-efficiency instead of pretty abstractions and virtual machines and template meta-programming.

It may not be a style of programming that agrees with you but it's one that has a growing number of proponents from Casey to Mike Acton, Jonathan Blow, and others. It's not a new idea either... but it certainly distinguishes itself as a reaction to the normative notion of programming by abstraction. It's a philosophy that proscribes programming by mechanical sympathy; using machines to manipulate data to get the results you desire.