> No one has come close to solving recommendation.
What if it isn't solvable? To me it doesn't look like there is enough room to maneuver, at least not in things like movies and TV shows, I think in music there might be. Say a recommendation needs to fulfill the intersection of 2+ things the user likes to feel like a recommendation, for example "you watched space and romance movies, here's a romance in space" otherwise it's just "you watched some space movies, here are some more". I don't think there are enough movies in existence, especially once you apply common criteria like "isn't in a foreign language, isn't on another streaming service, isn't very old or low budget" for these intersections to be filled with more than one or two items. In the space romance example above, the sole example I'm aware of is Passengers, there may be one or two others but it's not enough that you aren't going to deplete the pool even watching casually.
That only leaves extrapolating completely new things I might like based on more general patterns, but that falls victim to the same issue. If you know that I liked Passengers (already difficult without explicit feedback, watched does not mean liked), you have no idea whether I liked it because it had Jennifer Lawrence in it, or because of the tone, or the presentation, or the theme, or any other facet of it. And I only watch tens or hundreds of movies, not the thousands or ideally millions necessary to isolate the fact that I like movies with one very particular tone very slightly more than other movies.