Sure, if everyone is an expert on the subject, or is willing to spend the time to become one, you should never appeal to authority.

That's not most people on most subjects. If someone appeals to authority and says "climate change is real, here's 100 scientists with PhDs who agree" I accept that. I am not willing to become an expert on the subject to be able to spend the time to review the facts for myself. Citing sources in a paper is essentially appealing to authority (I understand I could read those papers and the ones they cite, all the way down, but for most things, I'm not going to do that).

For what it's worth, for a specialist in a field, they'll have already read most of the papers that are cited and will be looking for new or missing ones to find gems or flaws in the argumentation.

That's fair. Most papers are probably written with specialists in mind, so I guess that wouldn't be a good example of appeal to authority.