He did a perfect thing...but it's mans free will that you are referring to. It's like you get a new car, it's perfect (so to speak), but if you don't take care of it, run it through the proper maintenance, etc.....it will not work for you......
If it's just a matter of maintenance, how come babies are born with serious genetic defects? This is not a matter of poor maintenance on the babies' part, or on the part of their parents. It's just random back luck.