“Most music is terrible” so I’m not particularly drawn to having this vast archive. I want to listen to the things I really like.

It’s also not lossless, so from an archive standpoint that seems to diminish its value.

That said, I do think the insights they post on their blog about statistics and distribution are interesting. And just because that music is currently available via paid services doesn’t mean it will always be as accessible in one place. There would be a lot of manual collection and labeling you’d have to do to get something like this otherwise. And you wouldn’t have nearly as much confidence about how comprehensive such a database was if you did it yourself.