Earlier quoted context omitted.
>but still - concepts are more important, you don't have to learn langs in order to be familiar with concepts You kinda do. Concepts are often exclusive to languages. And often concepts can't be internalized without practice of that lang. Your own examples in your edit literally contradict what you say as you chose langs with extremely divergent concepts. C# and Erlang, Rust and C. You missed haskell and lisp.
>Your own examples in your edit literally contradict what you say as you chose langs with extremely divergent concepts. C# and Erlang, Rust and C. You missed haskell and lisp. How so? You can learn and understand concepts implemented in Rust without learning Rust
If the only tool available is rust, then one must learn rust to truly learn the concepts related to it.