You're basically saying the average developer is grossly incompetent. Which I don't necessarily object to, but it's important to be aware that this is what you are saying, even though you are not using the exact phrase "grossly incompetent".

If the average developer is so incompetent maybe they should undergo further training before being allowed to touch production systems? I suppose this is what code reviews are for, but I don't see how it helps when incompetent developers review each other's code.