Well in my opinion, the goal of a composition is expression, whether it be emotions or abstract ideas being expressed. Or sometimes the composer might just want to realize a certain sound he/she likes.
As for language vs. music, I think that language is much more "applied", in the sense that it is used more as a tool for communication than a medium for self-expression. Languages can be diverse though, C++, python, Java, etc. can also be considered languages, but overall it seems like language in general has more rules and axioms than music (sentence structure, grammar, syntax, what have you) and is somewhat more limited than music. So I'd say that there are certain things music expresses that language can't, or at least can't express as effectively (eg. background music in horror movies project fear more effectively than a narrator describing the scene).