I have been on the other side of table where a coworker told me that my code was complex. But at doing that he appreciated the code that it worked as expected

I have been on the other side of table where a coworker told me that my code was complex. But at doing that he appreciated the code that it worked as expected and how quickly I made it work, he taught me that in long run though, how a complex code would lead to various bugs. Show him examples, show him how to refactor that and convert the same code into a beautiful code. So, my advice would be to give something back to the developer in case you want him to listen to you.