Movie summary channels are a viewership machine if you do them right, people love consuming stories in short bursts, and the three to eight-minute format with intriguing titles works best, an eye catching thumbnail with close up faces and large text also adds a lot.
The problem has always been monetization through copyright, but the key is adding value, it's not enough to just include the scene, you have to analyze the character's psychology or the scene's context, if your voiceover is original and you offer a unique perspective, it's considered fair use, the channels that survive today are those whose owners truly know about film, not those that just cut scenes.
In addition to advertising, you can diversify with memberships for extra content, t shirts with iconic quotes, or affiliate links to platforms where you can watch full movies, if your niche is horror or science fiction, which have very loyal communities, take advantage of that, people will never get tired of being told stories, you just have to find your own angle.