Here's what a code review is like: someone sends you a puzzle. When you can't solve it immediately, you feel lazy or stupid when you tell them, "hey, thanks for going out of your way and solving that tricky problem for us. But you're not done yet. I want you to make this puzzle simpler, because I don't want to deal with it." You feel like you should either buckle down and solve the puzzle, or pretend that you solved it, because who will know you hadn't? The new code seems to work and there are far worse puzzles already in the project, so what's the big deal? It's hardly fair, right? Why stand in the way of progress? Why be the bad guy?
And yet pushing back is the right thing to do, because if you don't push back, everyone after you who wants to understand the code will have to solve that same puzzle again.