There exists no single tool that is best for everything.

Also, not every company can hire best developers (even though most claims so).

Imagine you are project manager for project X which is pretty mundane backend with pretty mundane API and you are given a deadline to develop it.

Will you:

a) try to find absolute best developers on the market and then use absolutely most powerful language (Lisp) to get it done?

b) try to find some developers that are available and use technology that is adequate enough that they can work with not shooting their feet off?

Take into account that you might not be able to hire best developers and even if you do, they might quickly leave not being satisfied with the mundane job you gave them.

Doesn’t beating the average require above average developers according to that article?

My experience is that you need a few developers who know how to use the technology effectively, and who are willing to mentor junior developers. Doing things like pair programming and code reviews goes a long way here.

Seems like that would be a good approach for a Clojure shop.

Honestly, code reviews and pairing are a good idea in any shop. These things significantly improve code quality and ensures that more people know what the code is doing.