I think the new languages are about developer productivity, but in a different way. It allows you to make more robust software via a better typing system, or more robust multithreading via rust's borrow system. In the past, our machines couldn't handle such strict languages as well because they have a high compile time cost.

In overall total effort needed to make something robust, something like rust will beat something like ruby, because the dynamic language-ists compensate via a larger test suite.