Would you consider this to be indicative of the quality of the C++ language? I think the standard library should usually be an example of optimal code with respect to performance, and when it is very complicated this would indicate, to me, that the language makes good code complicated.

If you look at an advanced C library, you'll see perhaps some odd tricks or nifty algorithms, but you probably won't see something that leaves you scratching your head about what the code is even asking the computer to do.