Not sure I get your point. One can definitely "get good" at problem solving. Isn't that the whole purpose of Leetcode and whatnot?

I struggled with Rust at first but now it feels quite natural, and is the language I use at work and for my open-source work.

I was not "mentally deficient" when I struggled with Rust (at least that I know of :v), while you could say I had a skill issue with the language