A lot of times if you say, "I'm having trouble understanding how module X does Y, and why it works that way." And the developer will say, "Yeah, I kind of hacked that together when the requirements changed. In a perfect world, it would get rewritten, but I've had a bunch of other things higher priority."
So you come to the code trying to understand why it is that way, and the developer will criticize it themselves.
And then you understand that you weren't wrong, and the opportunity for improvement is there, when time is available, but you haven't risked alienating people by treating them as if they're idiots for writing imperfect code.
So you come to the code trying to understand why it is that way, and the developer will criticize it themselves.