This is more a reflection of where the compiler is at, not the language. As a compiled, strongly-typed language without a GC, there is no theoretical reason why Rust could not be faster than C++. As the use of MIR and HIR (two intermediate languages used within the compiler) increases more optimizations taking advantage of the memory model could be added.

In the current state, much of that work is left to LLVM which is designed more around the C/C++ memory model and only some of the ownership and aliasing information can be represented in that form.

I am not arguing that Rust is faster now, only that it can be without fundamentally changing the language.