I'm possibly being naive with this question:

Isn't this a cultural, organizational problem? You said your original developers left or moved on to management and your new hires are rather inexperienced. Wouldn't it be a wiser long term strategy to facilitate learning and knowledge retention through mentoring, documentation, teaching and attractive technical career tracks?

For example there are several popular open source libs/solutions to manage application state and structure declaratively. And it is well known in the Clojure community that macros are a double-edged sword and should be used to solve specific problems.

I agree that Clojure is kind of a second (plus) language. But I also think there is a reasonable path from writing simple Clojure to wielding the more powerful features.