I think there is an in-between ground not covered by your comment. Good languages tickle (some class "foo" of) programmers in ways that tend to expand their rep

I think there is an in-between ground not covered by your comment. Good languages tickle (some class "foo" of) programmers in ways that tend to expand their repertoire. Many of those expansions enable better approaches to system design. It may be true that "experts" could do it even in Java, but many "foo-level" programmers would just do it the Java-way in Java, but can appreciate the better features of a better language in context. It's also probably true that many programmers will struggle with foo-level features. That harkens back to Vanier's LFM and LFSP essay: http://www.paulgraham.com/vanlfsp.html http://www.paulgraham.com/vanlfsp.html. Having seen LFM approaches to systems over the years, I'm skeptical that it is the right approach for anything with much complexity. YMMV.