I don't understand how it is completely unproductive. Surely there must some advantage that Rust has over C++? If that advantage exists then there is your justification for reinventing something that already exists. If all you do is reuse existing C++ libraries in Rust then why even bother with Rust in the first place? Why not just use C++ directly? Well, the most of the value from using Rust is derived from the things that are written in Rust.
Let me give you an example but this time with Groovy. Groovy runs on the JVM and that means it benefits from the existing JVM ecosystem, right? Well, of course you get the benefit of existing libraries but there was a crucial difference between using them through Groovy/Grails than natively through Java. There were lots of grails plugins that were very thin layers above the Java libraries yet somehow the usability increased a hundredfold. A small plugin with maybe 1000 lines of code ended up providing more value to our business than the part of the library that was written in Java.
Let me give you an example but this time with Groovy. Groovy runs on the JVM and that means it benefits from the existing JVM ecosystem, right? Well, of course you get the benefit of existing libraries but there was a crucial difference between using them through Groovy/Grails than natively through Java. There were lots of grails plugins that were very thin layers above the Java libraries yet somehow the usability increased a hundredfold. A small plugin with maybe 1000 lines of code ended up providing more value to our business than the part of the library that was written in Java.