People who dwell on the past annoy me. Specifically, past technologies. I think there's a certain sentimentality about things that needs to go out the window if we're to progress as a species.
Things like letter writing, paper books, the "absolute necessity" of face-to-face contact for human relationships, factory farming (obviously), the superiority of human labor, and high regards for organized religion are all obsolete. I know that sounds exactly like something that someone of my generation would say, and, well, hey, that's the point! That's okay! Things are evolving. So when people stick around on the past, on ways of doing things that are costly to us or the planet, I get annoyed.