Whenever my partner and I watch a movie we enjoyed we'll search up threads for it on Reddit because there's always people discussing recommendations of similar films, or at least movies that people who enjoyed the other film liked as well, to add to our backlog.

Works especially great for horror movies, for us at least. I don't always quite understand why I may have vibed so well with a particular horror film since they can be so hit-or-miss between individuals, but other people who are more genre-savvy will be in the comments to explain it to me and have some great recommendations :)