I think the key difference, if we're being pedantic, is saturation makes me think of the movie industry competing against itself (e.g. putting out too much product). But the studios aren't just competing against each other. As you mentioned, they're competing against YouTube, streaming services, video games, watching other play video games (which is a thing kids do for some reason), social media, etc. I think it's an important distinction because they aren't going to increase the value of a movie simply by releasing fewer movies.