It's all bug fixes it seems. What is surprising is that so many bugs remain even after all this time and effort. And no, for the most part these are not the kinds of bugs that are squashed by a rewrite in Rust.
Things have changed quite a bit in the past 30 years!
I encourage you to peek at their changelog (https://www.sudo.ws/releases/changelog/) for more insight into why this project is still under active development.
Isn't it done and finished, after 30 years of development?