I try to always rewrite complicated code. As an example, another dev who left the team had written a program in Elixir that nobody knew or understood. I rewrote it in python (with his help, since I still had contact with him over chat). After that, everyone in the team could understand the code and we could make changes very easily to it and document it.

Another program he wrote in python was kind of complicated and we would have bugs in it that we didn't know how to fix. So I rewrote it with a completely different architecture with focus on simplicity. And again, now everyone could just read the code and understand it.

I think many devs are writing code that is not simple to understand for others. Then rewriting it can be worth it to avoid the pain of trying to fix bugs in complicated code.