I think learning a programming language has similar logic/intuition that learning natural languages has. That is, learning a language that you actually use is much easier than learning a language you don't use. So for instance, if you just read tutorials / grammar books and never actually solve problems / communicate with people you will have a harder time. It matters less how difficult the language actually is -- you can easily spend months or even years wrestling with those tutorials without getting beyond a beginner stage. Then you get some motivation to actually use it for something and you advance in weeks more than you advanced in a year before.

Rust especially, thanks to the efficient hypemachine, will have the problem of people wanting to learn it but not having anywhere to apply it immediately. I actually have a similar problem with French.