The learning curve is quite small. You're just learning a different thinking process than you're used to.
It might help for you to read "The Roots of Lisp" by Paul Graham, which will not only explain Lisp's core axioms, but also show you how they form other things in the language.
After that, I'd see if you can find a copy of "The Little Schemer" by Daniel P. Friedman and Matthis Felleisen, which will not only introduce you to sound functional concepts through the use of recursion, but do so by helping you write functions which are actually quite useful.
There is of course, much more literature out there that will go far more in-depth into Lisp, but these will provide a gentle introduction to the basics.
The learning curve is small if you have a math or cs education, if you've been exposed to another functional language or you naturally think in s-expressions.
If you are just a random python programmer and you looked at arc I could see it being challenging. The axioms of lambda calculus and functional programming are concise and simple but that doesn't mean the concepts they imply are also simple.
I agree The Little Schemer is a great book. Along with SICP, On Lisp, etc.
In the end it is worth the trouble to learn at least one lisp dialect. It'll improve your coding and make you question why you are writing imperative-language-001 all day long.
