I think it indeed heavily depends on your marginal return in reducing bugs. I agree Rust is unsuitable for most software, because rightly or wrongly, bugs don't matter in most software.
Some of the bugs that Rust prevents do matter in most software but only occur in languages without GC.
In my view, Rust has a good chance of gradually replacing C++, because C++ devs don't shy away from using a large, complex language, and they can appreciate what the borrow checker does for them.
Yeah, that's where I use Rust now, where I previously would have used C or C++ (and if I previously needed C I always used C++ with extern "C".) These are places where I can't use Go because I need a language without a heavy runtime.
I use TypeScript for the browser and React native, because that is much better done in JavaScript land.
In my view, Rust has a good chance of gradually replacing C++, because C++ devs don't shy away from using a large, complex language, and they can appreciate what the borrow checker does for them.