Anyone can argue that any language is efficient based on some ability to express a (relatively) complex idea in (relatively) few words.

In Sanskrit, for instance, one can express entire metaphyiscal/philosophical systems in a single word, using compounds, and in philosophical commentaries this is actually quite frequent (which is what makes reading philosophy in Sanskrit so difficult, because everything is so condensed). The compounds can be of an arbitrary length, and feature extraordinarily complex syntactic system that allows for such complexity of expression. See the Wikipedia article below, for more.

https://en.wikipedia.org/wiki/Sanskrit_compound