Given that we've now got a three way language schism, the story for sharing data between processes isn't really solved. Data can move nicely within Go, but not between Go and Rust or JS. Tools like ts-morph also got left behind with no replacement.
I think that in retrospect the power of the JS ecosystem was all about plugins. It's plugins that make ESLint such a powerful platform that it still can't be replaced.
From the perspective of making a efficient platform for running plugins, JS actually is the most theoretically efficient implementation language! That's why, for example, VSCode put a bunch of work into moving its core state from C++ to JS, a change which brought them big perf wins and helped them beat out Atom: https://code.visualstudio.com/blogs/2018/03/23/text-buffer-r...