Idk maybe it's because I did freelancing for quite some time and was often hired to clean up somebody's mess, but I think it's not so bad to rewrite someone else's code. What I normally do is quarantine the old code behind a clean interface, or else start fresh with a better code structure, and then copy and paste the good bits of business logic from the old project into the new one.

Code has a lot of really great properties which make it easy to modify in provably safe ways if you know what you're doing.