OS kernels? Everything from numpy to CUDA to NCCL is using C/C++ (doing all the behind the scene heavy lifting), never mind the classic systems software like web browsers, web servers, networking control plane (the list goes on).
Newer web servers have already moved away from C/C++.
Web browsers have been written in restricted subsets of C/C++ with significant additional tooling for decades at this point, and are already beginning to move to Rust.
Newer web servers have already moved away from C/C++.
Web browsers have been written in restricted subsets of C/C++ with significant additional tooling for decades at this point, and are already beginning to move to Rust.