Re: Umm
They could create one. I am not saying they have to, but even if I argue for the point they made, your objections don't apply. They did not ask for Rust to be the IDL used by operating systems. They said that C wasn't good at that purpose and could be improved. Since Rust takes a lot of its influence from C, it's likely it wouldn't be great at it either. It's not new to use a language for interfacing that wasn't used in writing the system, and other operating systems have done it.
"It seems weird to me that C provides a way to call into C, *and* a way to call out of C, and gets criticized because the language it uses is C."
C doesn't have ways to call out of C. Other languages link to C stuff and call in, but you never see a C program directly linking to Java or Python. It can link to libraries written in other languages that have chosen to have a compatible format, but in each case, the other language has to change itself to match C. If a C program contains a component in something that doesn't follow the standard C linking structure, a different interface language is used for that connection. This doesn't make C bad. It makes your compliment wrong.