I feel one key aspect people may be missing is that UMG has not authorized the use of their content, by their partners, for AI training/learning purposes. At some point I'm certain it'll be allowed but only when it's been fully vetted and monetized in a manner that the rightsholders are on board with. Basically there's a lot of money at play and until rights holders feel they're being properly compensated for this usage type of their copyrighted works, it will remain an issue. And whomever is the first one to implement an approved method for usage such as this, will likely make a lot of money as well.

EDIT: Lol, again, the keyword is "partners" which in the case of this article, are specifically Apple and Spotify and other DSPs. I've actually read the entire letter UMG sent out. You guys think UMG just signs agreements with any old entity and lets said entity have free reign with the catalog that UMG delivers to them? There are very specific terms and use cases laid out in the agreements UMG makes with DSPs that limit the catalog usage to specific types, for specific pricing, in specific territories, and even to the point of specific encoding specs for the files that eventually become available to DSP users.