Is it about intelligence or just not being used to/having time for learning a different paradigm?
I personally have used LISP a lot. It was a little rough at first, but I got it. Despite having used a lot of languages, it felt like learning programming again.
I don't think there's something special about me that allowed me to grok it. And if that were the case, that's a horrible quality in a language. They're not supposed to be difficult to use.
I think it allows very clever stuff, which I don't think is done routinely, but that's what gets talked about. I try to write clean functional style code in other languages which in my book means separation of things that have side effects and things that don't. I don't think I'll have difficulty writing standard stuff in Lisp with that approach.
Just because it allows intricate wizardry doesn't mean it is inherently hard to get/use. I think the bigger issue would be ecosystem and shortage of talent pool.
