C and Unix have stood the test of time. It has been 50 years since they were designed, this is a long time in terms on computing. It is not unreasonable to think that they will stay for another 50 years.
Yes, they SHOULD be adding Fortran, another language that has stood the test of time, to the Linux kernel.
Or... Maybe it's good that they add a new (still 10 years old) language with security and DX improvements occasionally. 50 years ago, that language was C...
Is it? Do you think it's hindsight to use the only "successful" story as "the only way forward?" Look at the gas vs electric vehicles. Yes, displacing legacy is hard but not insurmountable when there is a clear improvement. I don't think anyone can argue in good faith the Rust is NOT an improvement in C.