Yes, sustainable business model is hard. Just look at Spotify's stock - it's basically break even since IPO. The music industry adjusts their fees to keep Spotify alive, but never significantly profitable, and Spotify has little ability to push back on this.
...but there's also soooooooooo much entrenchment going on in this space. There's special contracts written that whitelist which platforms tracks can be played on and tricky "favored nation" clauses (https://www.nytimes.com/2015/05/25/business/media/sony-terms....) So, if you create a new platform, and it's a real threat to the others, then you just get denied a seat at the table unless you make concessions to the point of impotency... or you only have indie music that struggles to attract masses.
Ultimately I decided that, while I cared a LOT about this sector, that it's just too much of an uphill battle.
Your idea sounds cool though. I wish you luck. Is it your intent to build a music catalog that is entirely unique to your platform, to bring in indie artists, or to try and bring in the big names, too? If you're not trying to bring in the big names... how do you prevent the situation where someone says, "I love this song, but next I want to hear ____.", it's not on your platform, and so they open Spotify/YT, and now suddenly you've lost engagement with your platform. I don't feel that consumers maintain playlists across multiple music services and bounce between them based on their current listening preferences. Do you?