I want to hear the perspective of someone who lost 100kloc and had to rewrite it all!

There is a lot of value in code. It works in prod. It is continuously regression tested by its load, so when there is a problem you figure out a tiny delta to fix it.

If you rewrite from memories you'll get a lot of bugs you need to fix again.

Code being worthless and "must keep PRs small" seem to be in tension.