The language is 100% capable. Matplotlib's API is horrible and confusing because one of their design goals was/is to be similar to matlab (that's where the "mat" in it's name comes from) to allow people who are comfortable with matlab to switch more easily.
Matlab's plotting facilities are a mess of global state, so matplotlib has copied it.
> An 'elegant' language would provide a way to do so without all of these leaky abstractions.
It would have to do something else, first: Exist.
In 10+ years of programming, I've yet to ever see a implementation of a complex abstraction that was comprehensive and complete enough that I didn't find a corner case requiring me to reach through it and deal with platform specific something-or-other.
I think I like Python, because coming from C, a lot of things that are tedious there are effortless in Python (Strings! Lists and dicts, libraries, and so on.)
That's why each and every number crunching problem will eventually make use of the various escape hatches to call libraries written in a language that is performant.
As for strings: BASIC also had strings. That doesn't mean that having strings (or even dicts) is what makes a language elegant.
The problem really is that there are only so many sweet spots for programming languages and usually those come with limitations with respect to the domain you want to use them for. Pick any two: expressive, fast, easy to use.