Before I answer all your questions let me say this, you can have the best idea ever it can be the perfect platform ever but if no one knows about it then its useless. I ran into that problem a lot when building this platform getting it out there building everything was easy the promotion was the problem. I provided a trending category on my platform before all the music platforms in my niche decided to incorporate it. I also used social media websites like YouTube to place my watermark on celebrities videos to drive traffic to my website. I even spent time building a database of artist, old underground unreleased music to catch the google results through SEO which worked but it still wasn't out there as much as I wanted it to. Now a days the biggest way to drive traffic is to get YouTube creators to promote it which isn't cheap and also social media platforms ads which also isn't cheap. But to answer your question about the algorithm ours was pretty simple so I can't recommend anything about the complexity you're speaking of which is a great idea.

Just don't be like me spending all my time on the code and not enough time figuring out how to sell it to the users