Grammarly is (was) written in Common LISP
https://www.grammarly.com/blog/engineering/running-lisp-in-p...
Given LISP was supposed to build "The AI" ... pretty sad than a dumb LLM is taking its place now
Grammarly came out before the LLMs. I'm not sure what approach it took, but they're likely feeling a squeeze as LLMs can tell you how to rewrite a sentence to remove passive voice and all that. I doubt the LLMs are as consistent (some comments below show some big issues), but they're free (for now).
Not that I think LLM is always better, but it would be interesting to compare these two approaches.