The expressive power of a language is definitely based on what's in the standard library. If the C standard library came with default dictionaries and other common data structures (while still allowing you to build your own) it would be a much more expressive language.

I love C, I love that I can keep most of the standard library in my head, but a greater built in eco-system would make portable code a lot easier, provide a standard reference to beat, and make the language more useful from the get go.