My read, which is based on context from elsewhere but could be wrong, is that the post is not really talking about creating a replacement for traditional shared

My read, which is based on context from elsewhere but could be wrong, is that the post is not really talking about creating a replacement for traditional shared libraries that works across language boundaries (like COM or Wasm components). Rather, "other languages" here is a euphemism for C++ in particular, and the goal is to enable incremental migration of brownfield C++ codebases to Rust. The goal of pervasive memory safety everywhere, especially in the kinds of contexts where C++ has traditionally been used, requires some kind of answer to "what about all the existing programs?", and the current interop between Rust and C++ is not good enough to be a satisfying answer. If it gets improved to the point where the two languages can interoperate smoothly at the source level, then I think the possibility of Rust displacing C++ for most use cases becomes something like realistic.