Your world seems small -- I never said anything about dumping codebases. If i have a library implemented in Rust, which gets called by a program written in C++

Your world seems small -- I never said anything about dumping codebases. If i have a library implemented in Rust, which gets called by a program written in C++ through FFI, and contacts a service which is implemented in python, I don't need to dump or waste any old work. A carpenter that only uses a hammer isn't a very good carpenter; different tools have different strengths and weaknesses.