Why would you rewrite it in rust? The engine is in C++. It's only the syntax part that's broken. So a new parser, new AST handling code, some engine section overhauls here and there to match the new reality. And they could even separate the engine from the syntax while they're at it, making it even more powerful. Simple? No. Necessary? Yes.

The alternative is to keep smearing more and more lipstick on the pig and hope people don't keep abandoning it, which is a shame because CMake COULD be great.

It's not only the syntax that is broken. The "type system" has quite a few holes in it because of the language. Many of them have no counterpart in other languages either. It would, for example, most likely still be stringly typed, so list representations would still get baked down into `;`-separated lists with all the problems that entails.