Today, I read a sentence on the Internet that a good photographer simply disdains high ISO. How to understand this sentence?

This is a photographer who can only do one kind of work. There are not many fields involved, and the quality of equipment in his hand can't be higher. It is a saying that he can't eat grapes. He encountered less, a certain environment allows you to complete a photography task, which is absolutely not allowed to use flash. What should you ask him to do?