that's smart. full disclosure i created exactly your app but like 8 years ago. exact same purpose. if i did it now (which you have), then one avenue to consider

that's smart. full disclosure i created exactly your app but like 8 years ago. exact same purpose. if i did it now (which you have), then one avenue to consider is crawling closed captioning from the youtube video. you should be able to 1) find interesting content and note it on there 2) allow people to search for a spot to go to based on the closed captioning. that sounds pretty neat actually now that i think of it 3) if you wanted to get a little risky, you could watch where people scroll to/pause/get started at from the time stamp query and use that to determine popularity at a certain spot in the video