We do not understand genetic code as code. We merely have developed some statistical relations between some part of the genetic code and some outcomes, but nobody understands the genetic code good enough to write even the equivalent of "Hello World!".
Gene modification consists of grabbing a slice of genetic code and splicing it into another. Impressive! Means we can edit the code. Doesn't mean we understand the code. If you grab the code for Donkey Kong and put it into the code of Microsoft Excel, does it mean you can throw barrels at your numbers? Or will you simply break the whole thing? Genetic code is very robust and has a lot of redundancies (that we don't understand) so it won't crash like Excel. Something will likely grow. But tumors are also growth.
Remember Thalidomide? They had at the time better reason to think it was safe then we today have thinking gene editing babies is safe.
The tech bros who are gene editing babies (assuming that they are, because they are stupid, egotistical and wealthy enough to bend most laws) are not creating super babies, they are creating new and exciting genetic disorders. Poor babies.