I am mainly saying it is suitable for solving harder problems than Go. Most problems are not hard; Go is good enough for them, and easier to learn and use well.

All these languages are Turing-complete. The difference is in how much work it is to design and write the program, and in whether it can satisfy performance needs.

C++ wins here by being more expressive, making it better able to implement libraries that can be used in all cases. Rust is less capable, but stronger than other mainstream languages.