I don't fully disagree with you but my personal opinion is that people give too little credit to contemporary movements within Western art music. Their cultural force is significant, but it's clouded so it's not easy to make an accounting of it.

- First, I need to note that although serialism proper isn't so relevant today, when it comes to film music dominant styles in the last couple decades or so have been minimalism and neo-romanticism. Neo-romanticism is obviously self-explanatory and well-understood, but minimalism [1] is harder to deal with only because it's a contemporary and peculiar style, and it's also rather controversial within Western art music community (especially since the kind of minimalism I hear in film music is closer to the style of Glass and Richter, and not Reich, Adams; or not even Ligeti et al's similar works such as "Selbstportrait mit Reich und Riley" (1976)). We can debate endlessly about the history of Western classical music, and I'm no art historian, but my personal opinion is that minimalism is a direct and clear response to serialism [2] which makes it a cultural heir. In art, we do see that things swing pretty far like a pendulum. What drives an artistic force in one direction can often be a previous force in the opposite. So, when you hear the soundtrack of something like Amelie (2001), in a way you do hear serialism, except in negative.

- Second, although the music of "the Second Viennese School" and later serialists (Boulez, Stockhausen) found no mass appeal, they did find sufficient amount of appeal within the music community. Serialism was practically the dominant style in early 20th century. Neo-romanticist composer David Diamond talks about his frustrations about this in this interview [3]. Given this, it's not true to state serialism has no cultural power, what's true is that most music produced today is one way or another post-serialist, in the sense that it's aware of its failed experiments and its merits. For example, music (film music/art music/whatever) today is not particularly contrapuntal, but composers are regularly, formally taught how to deal with counterpoint and it's considered a core skill for all composers. This makes composers skilled in this regard, but they consciously decide not to apply the full length of the skill. The same way painters are taught to draw like the old masters, but that kind of photographic realism doesn't have the same cultural relevance today in art. This still makes Bach (or old masters) culturally relevant today, albeit rather indirectly.

- You call that the rules were contrived but that is one particular interpretation of serialism, which is fair only because it's similar to how Schoenberg thought of it. However, if you look at other serialists such as Berg, Webern, Boulez and especially Carter, you'll see that the kind of "use each pitch once before using all others" silly rules are not taken any more seriously than you take counterpoint rules seriously while writing music (which was the source of disagreement between Boulez and his teacher Leibowitz [4]). Those rules are for practice. It's debatable, of course, what is "serialistic" about serialism (especially for later figures like Carter), but I think the core of the idea is for musical language to be comprehensive, and have a presentation of all possible forms of a given set of structures. Given this understanding, I don't think your statement "the rules were contrived rather than evolved" holds up. Within the tradition, there was the understanding that the way tonality evolves is that each composer comes and creates their own spin on the diatonic scale, all the way from Froberger to Bach to Chopin to Debussy we keep seeing this pattern again and again. Serialism has a will to go one step further and present all such possibilities in music. Again, I don't shy away from calling this, in many ways, a "failed experiment" but calling it "contrived" is not true.

[1] Example movies are countless, from Amelie (2001), The Shape of Water (2017), Blindness (2008) to Ladybird (2017) etc...

[2] Philip Glass talks about how his music is a response to Boulez scene (who is a late serialist composer) in this interview from 1976: https://www.youtube.com/watch?v=elAtF6UdefI

[3] https://crisismagazine.com/vault/americas-greatest-living-co...

[4] https://fugueforthought.de/2016/07/13/boulez-piano-sonata-no...