I have a science background but am fairly new to film critics and what they talk about.
In science, references are used to support statements, introduce some ideas that other scientists may propose, etc. They have a purpose. So, you can kinda imagine my reaction when I first came across references in movies a few years ago.
I remember one youtube film critic talking about a scene in New Nightmare (1994) and how it 'referenced' Nosferatu (1921). Basically, a scene in which Freddy comes out of a bed and stalks across a bedroom, throwing his silhouette on the wall reminded him of the Count Orlok's silhouette. Er, and that's it. I remember asking myself at the time, what purpose do film references serve?
And I still haven't found the answer, lol. One issue here is that film references and themes are a bit like seeing shapes in clouds or looking at a map of Australia and Tasmania and seeing a rabbit eating an apple. You see what you wanna see.
E.g. another youtuber claims that The Hills Have Eyes (1977) gives a commentary on the Vietnam War. After I'd stopped laughing, I thought, Does it? If it does, it's an extremely shallow commentary. XD
Critics even see themes that the director of a film hadn't intended. A great example of this is The Fly (1986) - some critics saw Seth Brundle's physical degeneration as an allegory for AIDS. Director David Cronenberg has patiently explained that this was never his intention but I'm not sure all the critics have taken his comments on board.
Of course, not all youtubers or other film critics waffle on about references or themes, some concentrate on the functional elements of a film - writing, plot, dialogue, acting, effects, etc.