@sir "However, its replacement will be simpler - not more complex." Exactly my feelings!
One thing I find surprisingly missing from the "why not rewrite it in Rust" conversations is that Rust is complicated. It changes the economy of programming: if you're able to write a program that works 98% of time in an hour then an extra hour for 99% may not be a good deal.
It also raises the bar: a more complex language needs a better brain, larger working memory. Biology just might not be on your side.