Watching any form of media with subtitles is a good way to learn English. It allows the person to hear it in their own language, but also be able to read it in English. And vice versa they can hear it in English and see how it said in their language, helping to break language barriers.
Typically，people spend about 2hrs to watch a movie, however, we might only learn a few new words. If we use that 2hrs to read 100pages of book, we'll probably broaden our vocabulary and even learn some useful sentence structures. Also, to improve our understanding of the cultures of English-speaking countries, we can talk to people from these place and while chatting face-to-face, know more about the usage of certain words( or phrases) and their cultures.