It’s actually a classic programmer move to start over again. I’ve read the book “Clean Code” and it talks about a little bit.
Appereantly it would not be the first time that the new start turns into the same mess as the old codebase it’s supposed to replace. While starting over can be tempting, refactoring is in my opinion better.
If you refactor a lot, you start thinking the same way about the new code you write. So any new code you write will probably be better and you’ll be cleaning up the old code too. If you know you have to clean up the mess anyways, better do it right the first time …
However it is not hard to imagine that some programming languages simply get too old and the application has to be rewritten in a new language to ensure continuity. So I think that happens sometimes.