I disagree, cppreference is pretty good. The information is very complete and useful examples abound. And just because you may not understand a template operator definition does not make it useless documentation.
I'll expand by saying I think there's two types of documentation: references and guides. cppreference is a really, really good reference. It's complete, highly specific, and well formatted.
But it's an awful guide. If I was trying to learn C++ or it's standard lib, I would want to kill myself.
The problem is these two types of documentation are almost perfectly perpendicular in my mind. Meaning, a good guide is a poor reference, and a good reference is a poor guide.
Hand-holding step by step instructions, popular with many js frameworks now, are great guides. But when I want to know what function X returns and under what circumstances, I don't want to prune through a guide that starts at the beginning of the universe. And often those guides will be missing huge amounts of detail to lower the complexity.
So you need one kind of documentation when you start, and then another 5 years later.
