Not even, it was my first functional language (other than about an hour I had spent playing with F# a few months before) and I managed to be proficient enough to read real-world code and able to write my own code in it. Overall, OCaml doesn't have any very difficult concepts that stop you from using it. Can't get currying? Just pass args explicitly, even use tuples for them. Don't get monads? Ignore Lwt/Async. Don't know about functors? Just don't write module-heavy code, etc. Overtime you can sort of start to grasp the other features, but it's not a language that takes months just to be able to use.
