Maybe a clearly published outline of where their language fits in the ecosystem of languages that are out there. e.g., it improves on these aspects of C++, gets

Maybe a clearly published outline of where their language fits in the ecosystem of languages that are out there. e.g., it improves on these aspects of C++, gets these traits from python, fixes these weaknesses of C, but doesn't improve on X, and Y is something that C still does better. Or something like that. Then there's something out there and clearly visible that immediately shuts down the zealotry because the maintainers have said exactly where Rust stands, and what they think it's great at, and what it doesn't do. Which seems like the problem: that the zealots are giving the impression that Rust is better than C for everything.