Even in the most egregiously over written adventures, I have never encountered one that asked me as GM to simply quote from it. There is a lot of decision making that goes into GMing even by the book.We should not confuse the ability to influence outcomes with the particular choice of how to do that.
The choice to closely follow a published adventure closely is still a choice, and thereby an exertion of agency. If the GM reads an adventure and thinks, "This written stuff is really cool! I want to make it happen," then making it happen is an exercise of their agency.
Plus, even while they are "quoting a book" (that phrasing sounds a bit loaded with assumptions, to be honest) there's a whole lot of space for the GM to shape events with exactly how they present that information, the detailed choices they make for NPCs, their rule interpretations and applications, and so on.
It almost feels like someone who.would suggest this doesn't have a lot of GMing experience, to be honest.