I'd argue that Rails' use of DSLs and metaprogramming makes it materially different from straight ruby. It gets even more confusing with lisp where your libraries are, by definition, language extensions. Often with completely custom syntax.

It's kind of an irrelevant distinction anyways. People don't really pick "languages", per se. They usually pick "language + libraries", and the line between third-party libraries and standard libraries is getting increasingly blurred.