I think this could be particularly difficult for people (just guessing here) who haven't used a functional approach in the past. The shift from procedural imperative thinking to functional thinking is not obvious, and Clojure strongly pushes you to use immutability right away, too. That can be a steep learning curve.

I can tell you that the payoff at the end is huge, though :-)

As a side note, I'd highly suggest that everyone reads "Seven Languages in Seven Weeks" (https://pragprog.com/titles/btlang/seven-languages-in-seven-...). There are many programming paradigms and opening your mind to them is a great investment in the future.