Nothing wrong with including some opinion, as long as you also answer the question properly.
This goes for pretty much any type of answer, not just story-ID. It's OK to include a little bit of more subjective discussion, or even humour and jokes, as long as the bulk of the post is focused on seriously answering the question. We don't absolutely "hate fun" ;-)
For story-ID in particular, there are several things we in general might learn from a Q&A as well as just providing the OP with their answer. For example, the question might show us which aspects of the story were most memorable, at least for that particular OP. A good answer will show how the given story matches each element of the question, but it might also be interesting to include some additional information, even if that's subjective. We're not a review service, but there's no harm in a little bit of opinion every now and then.
In this case, you provided a decent answer to the question - quoted plot summary, link for further reading - and then finished off with literally four words expressing your opinion of the film. I don't think there's any problem with that.