Rust is a better C++ more than a better C, it has similar goals to C++ of advanced zero-cost (at runtime) abstractions, not so much of being a portable assembly. Like C++ it can be an alternative to C in some contexts.
D intended to be a better C++, but that hasn't panned out well in practice for various reasons (one of them being the use of a GC and much of the standard library depending on it, though IIRC they're trying to fix that).
[1] For some purposes. As a long-time Pythonista, I've looked at Nim, and I have no desire to replace Python with Nim in my daily use. But my uses for Python aren't the same as everyone else's, and Nim looks like it could be a fun language to play around with and learn, at least.
[2] Even more accurate, Nim is a better Object Pascal.