That position about The Exorcist is ridiculous. It’s what happens when someone is used to one style of media, and can’t shift to appreciate media in another style. Like people who aren’t used to a genre of music or literature, and just think all genres dissimilar to what they are conditioned to, are bad.
It’s very common for currently younger people to not have the attention span to appreciate movies from 30+ years ago which had slower pacing and expected attention to detail, used actors more reflective of the general (older, less thin, less beautiful) population, and yes, did have less special effects technology, and sometimes were not very tightly directed or acted, and often required different types of suspension of disbelief than current films tend to.
I tend to have the reverse issue. I’ve seen and enjoyed many older films (including some of the earliest films), and I’ve very intolerant of newer films’ fast pacing, shuffling or narrative order, and what seem to me like intolerable levels of stupid writing, illogic, unbelievable characters and situations, and general lack of depth, quality and originality. (And also how so many actors are all ridiculously groomed and have million-dollar homes and wardrobes…)
As for the general question of whether “all of film criticism is subjective? Are there any aspects of film that are objective?”, I would say NOT all are subjective. What’s subjective is what one likes or finds interesting. But there are objective observations too.
There seems to be a really disturbing number of people who don’t get that distinction, and will argue with/about other people based on that. The version I’ve been appalled by most (which is different from your case) are the people who think that illogical lazy writing and plots that don’t make sense, can’t/shouldn’t be criticized for that, because they’re stuck on thinking that all criticism is subjective opinion, or that any fiction with any fantastic element doesn’t have any reason to have any of the rest of it make sense or even be self-consistent.
Whether you like the Disney Star Wars sequels or not is perhaps a matter of taste and opinion. Whether they make sense or not, or are consistent with the previous Star Wars films, seems to me objectively a case of no, they don’t/aren’t. Whether you find that as awful as I do is subjective. But they are extremely illogical, and I’d say it’s objectively true that the people who paid attention to details and continuity in the original Star Wars films were taking things much more seriously, where the sequels don’t really even try to care much at all about continuity or making sense. The people who like those films don’t care, don’t get it, don’t think about it, don’t really know or appreciate the original films, and/or short-circuit to arguing that all opinions about films are subjective, or that all fantasy doesn’t have any reason to make sense about anything.