Don't feel that way. This is a highly specific role with a ton of not-necessarily-connected tech. Python, C++, Rust and calling out Java? Strange. You don't need to know any of this stuff to be successful. If you just know javascript, that's enough for many, many roles.

Youll find that if you understand the patterns you're using in JS, you can apply them to many other languages. Other languages will have different syntaxes and maybe slightly different patterns, but you can always apply what you know, which will make it easier to add more languages to your arsenal.

You'll feel like you have no idea what you're doing for a long time, but all the while you have picked up a ton of knowledge and experience that you will still probably discount. Just be eager to learn and don't sell yourself too short.