Name a program you can write in <language> that I can't write in <language> is a terrible way to compare languages. That applies for any Turing complete language, but I wouldn't write a game in emacs lisp.
> Go is more "limited" than Go
Assuming you mean "go is more 'limited' than rust, you can write all software in both languages. I'm not sure who claimed it either because both the linked article and comment above you don't.
The justification for C++/Rust is largely the same as the justification for any lower level language: performance. Theres a lot of cases where GC pauses are a no go (pun intended). Well written rust is going to be more performant than well written go. You have greater control over threads, for better or for worse.
The benefit of rust in particular is the approach to memory management, package management, and how hard rust it is to shoot yourself in the foot. Rust filled a gap where people wanted a performant, expressive low level language without the memory hassle that came with c/c++.