Syntax can certainly be more or less suitable to a particular problem or even to humans in general, but (dis)allowing identifier shadowing is part of the semantics of the language (i.e. what the syntax means). One could say: "there should be syntactic cues if we are to allow variable shadowing". That would be a well-defined criticism of syntactic issues. BTW, most modern languages do allow identifier shadowing. The particularity of Rust and the object of your criticism is allowing it in the same scope as the definition.

But again, the only way you'll be able to apprehend array language notation is by writing enough of it to become somewhat fluent. It doesn't mean you have to like it, but remember it was the object of a Turing award and that's usually a good indicator of something relevant.