This is not true. People who fix cultures are called "leaders" and the good ones do it every day, little by little. Chisel at the marble slab and eventually you'll sculpt a masterpiece.
Depends on the state of the culture. It has to be at least "fixable" with somewhat open-minded people at the top. There are 10x more people who try to fix cultures but end up burning out and being a scapegoat for everything.