I made a tool to export YouTube subtitles directly into Anki without downloading the video, it must be useful since it even got me a job offer by one of the users (pretty famous person). I never did more marketing than a Reddit post when the proof of concept was made. Coincidentally, I've worked on it recently and added some useful functionality. Extension: https://chrome.google.com/webstore/detail/youtube2anki/boebb…
What made you build it? It looks like one would use it for learning a language... mapping written text to pronounciation on flashcards? Why do you think making your own cards from YouTube subs is better than dedicated language apps that already include spoken audio?
You described the functionality perfectly, I made it as a tool to have custom cards for practising languages without having to be locked in any platform, in my opinion language platforms are very bland with their spoken lessons and only have perfectly pronounced sentences, with the tool you can practice more real and engaging topics for yourself.
Another usage that some users commented was to use it as a learning tool for lectures and presentations, that's why I included a merge subtitles functionality recently, so the cards can hold more information as opposed a single sentence.