I think it depends. If the original author (or most recent modifier) is available then "I don't get this code" means I should be scheduling some time to talk to them.

If the original author is completely unavailable and I am the new maintainer, then "I don't get this code" might be a valid reason to rewrite it. Even if I can't improve it, by the end of it I will know what those pitfalls are and understand that code.