Note that he says the most powerful language for the job. Which language is the "most powerful" varies greatly by application, and would include mainstream languages in a variety of contexts. For example, C++11 is the power language of choice for databases engines, and a reasonable argument could be made that languages like Python and PHP are as well in certain contexts. On the other hand, some application domains are arguably better served with esoteric languages.

In other words, use the best tool for the job. LLVM IR also deserves mention for its role as a kind of ur-language that can express all others in many modern applications. The ability to easily design and dynamically compile purpose-built languages is proving to be useful in many contexts.