In some ways I think Rust is a bad replacement for both. It's an alternative in some ways to C and an alternative in some ways to C++.
I don't think anyone who still uses C today and hasn't lived in a cave for the last 20 years would be very interested in Rust since it's just not at all like using C. There is the rare Bryan Cantrill who for some reason was seemingly unaware that other languages existed from 1990 until 2018 but I think it's safe to say most other people who primarily use C would not prefer the leap to something like Rust.
For the people who use C++, certainly they're already used to a language that wants to dominate, so Rust should be fine. In terms of features, apparently it doesn't hold up, but because it's like C++ I'm sure they're just a couple of years away from adding those things too, and then the language can continue being more important than the actual data transformations the programs are supposed to be doing.
> but because it's like C++ I'm sure they're just a couple of years away from adding those things too
If they're smart (which they are), I'm sure they'll eventually cave and add some of the missing stuff, no matter how much they want to believe these features are unnecessary. Just like how C is finally coming around and adding generics and all that. The particular capabilities I mentioned here wouldn't be impossible to add, and they can probably achieve some of them better than C++ did. But I do think there will remain use cases that Rust will fail to accommodate.
I don't think anyone who still uses C today and hasn't lived in a cave for the last 20 years would be very interested in Rust since it's just not at all like using C. There is the rare Bryan Cantrill who for some reason was seemingly unaware that other languages existed from 1990 until 2018 but I think it's safe to say most other people who primarily use C would not prefer the leap to something like Rust.
For the people who use C++, certainly they're already used to a language that wants to dominate, so Rust should be fine. In terms of features, apparently it doesn't hold up, but because it's like C++ I'm sure they're just a couple of years away from adding those things too, and then the language can continue being more important than the actual data transformations the programs are supposed to be doing.