When Jewish characters (for example) are on the screen, does the audience get more than an occasion reference to Chanukah? Or do they just get a surname, or a trope? Or worse, do they get thinly-veiled anti-Semitic caricatures? Are LGBTQ characters defined by their sexuality, or are they stereotyped, or is it no big deal? Or are they killed off quickly, once they're no longer useful to the plot, the show runners, or the network?
No matter how bad your review is, it will still be listed on your reviewer page on Amazon (yes, they exist; just click on a reviewer's name). This is a small spreading of news/linking back, and it will be helpful—almost no matter what you say. Almost.
Because this is not a negative review, you can add some length to it. But because it's not unremittingly positive, it does not have to be lengthy. The ideal length is probably about 50 to 100 words. If you want to say more, contact the writer in private. For self-published works, editing and republishing are usually pretty easy. Hence if you find a glaring translation error, the writer can fix it. You can save the day with your review.
Yet another thing to think about concerns the making of films. When films open, they are huge collaborative efforts which include not only the writers, actors, makeup and set people, special effects, the director, and the producer. They are also a product of budgets, and of timing. When a tragedy occurs, a film might be delayed, or even shelved indefinitely. And the same thing can happen if the star dies or becomes embroiled in a scandal. Furthermore, some films would benefit from an update in special effects technology. And others would change with our current social sensibilities regarding feminism, LGBTQ rights, and other issues.