I get it but in this context "authority" means an authority on a particular topic, not like a police officer or something. Appeal to authority becomes a fallacy when you appeal to someone who is not actually an authority on the subject at hand.
It's sort of like seeing a lot of arguments that rely on false or misleading evidence and deciding that "appeal to evidence" is a fallacy. The choice of authority or evidence is the issue, not the act of appealing.