It was written for a different type of developer and a different type of development environment and a specific language, C++.
You haven't looked at C++ lately if you think it's the same as it was in 2004. The ISO has released new versions of the language in 2011, 2014 and ratified a new standard here in 2017. If you're writing C++ code that is consistent with 2004 C++ then you're writing a really bad version of "C with classes", not C++.
Edit:
Modern C++ contains native support for the filesystem, threads, lambda expressions, variants, upcoming networking library, coroutines (at least in Visual Studio), no more new/delete memory management, parallel algorithms and a ton more. This is a completely different language now and the code you write looks nothing like 2004 C++ code.