Rust is intended to be a systems language capable of replacing C++ in its niche, and interfacing with existing C++ at a fairly coarse-grained level like Firefox

Rust is intended to be a systems language capable of replacing C++ in its niche, and interfacing with existing C++ at a fairly coarse-grained level like Firefox's oxidation (though cxx is trying to enable rich interop passing richer types than C-ABI ones), so it's trying to be a better screwdriver more so than a hammer. So difficulty expressing C++ concepts is arguably a flaw, and difficulty implementing all software with the same CPU/memory overhead as C++ (which I'd argue is the case, though some would disagree) is definitely a flaw. It's like creating a new screwdriver bit or handle, trying to convert the world to it, then attracting a legion of followers arguing that manufacturing flat-head screwdrivers should expose you to legal liability for anyone who slips it out of the socket and injures themselves (ignoring that flat-head screws existed and will continue to exist).