If one day medicine advances to the point where organs can be replaced at will, then surgeons can cut as much as they like. Is that even possible? Creating organs is basically playing creator, it's too godlike; with the level of science humans have right now, that goal is a bit too far off. Better to focus on how to develop drugs that can keep killing tumor cells more quickly.
Same logic: where are you going to find a big missing segment of esophagus to patch into a case of esophageal atresia? The only option is to let the child hurry up and grow their own organs longer to make up for it. Note, this "growing organs" doesn't mean the esophagus can grow back such a long missing segment. What doctors are hoping for is that with good nutrition, the other organs can grow bigger.
To grow organs you need nutrition, but with the esophagus blocked, no nutrients are getting down into the lower digestive tract.
