> I don't believe there's anything you can do in C++ that you can't do in Rust.

I think you'll have to make "can do" more precise for this question to have a meaningful answer. All mentioned languages are Turing complete and thus equivalent on that level.

> you can't access raw memory.

I can wrap a file in a ByteBuffer in java and the JVM will (make a best effort to) perform native I/O on that. Does that pass as "access raw memory"? If not, you'd have to explain how this is different from the abstract machine that C++ is defined on.

Sure, in Java you can't escape the garbage collector, but in C++ you also formally invoke UB if you violate the object lifetime requirements (even though will generally work due to this part of the standard still being... work in progress, let's say).