One of the issues I have with C++ is the standard library source seems to be completely incomprehensible.

AAAAAAhhh I once read a Stroustrup quote essentially going "if you understand vectors you understand C++", thought about that for a second, coming to the conclusion "surely he didn't mean using them, but implementing them", then had a quick google, people said llvm's libc++ was clean, had a look, and noped out of that abomination instantly. For comparison, Rust's vectors. About the same LOC, yes, but the Rust is like 80% docs and comments.