How far back is your time machine going to take us? Keep in mind that most of the structures that burned were over 30 years old, many over 50, and a good percentage over 70.
Or are you under the delusion that changing the building code somehow magically brings existing structures up to date? Not that it would make a lot of difference in this case ... Eyeball Wiki's entry on "Tubbs Fire". Nothing could (or did) withstand that. Not even homes that were built with the most up to date and modern fire prevention techniques.