"Most of them will choose a language that does x over a language that can easily be extended to do x, even if the library that provides x has already been written."
I nominate Ruby as the first "your language features are my libraries" language to become legitimately popular. This is likely due to the fact that Rails provides the libraries that most web programmers want, in addition to the cool language features. But it also seems that the "Rails community" is enamored with how easy Ruby's flexible syntax makes it to extend the language in interesting ways. Thus, all of the fuss over adding methods to base classes, and whether or not, or when, it is a good idea to do so.
So I would say that Ruby has brought the idea of language features as libraries into the mainstream, as much as anything as geeky as programming languages can be considered mainstream.
I nominate Ruby as the first "your language features are my libraries" language to become legitimately popular. This is likely due to the fact that Rails provides the libraries that most web programmers want, in addition to the cool language features. But it also seems that the "Rails community" is enamored with how easy Ruby's flexible syntax makes it to extend the language in interesting ways. Thus, all of the fuss over adding methods to base classes, and whether or not, or when, it is a good idea to do so.
So I would say that Ruby has brought the idea of language features as libraries into the mainstream, as much as anything as geeky as programming languages can be considered mainstream.