I'm as big an Apple fan as you'll find, but... Apple IS in the streaming music business, and they're both a provider of Spotify service via the App Store, and a competitor with Apple Music. Some of Spotify's complaints don't hold true, but some do.This narrative about calling Apple a “monopoly” is just so wrong. The App Store is a platform with millions of apps, and there’s plenty of competition. If Apple made every app, they’d have a point.
Spotify isn't like Uber or Deliveroo, the item being "Purchased" is delivered directly through the app - so Apple does deserve a commission. 30% the first year and 15% thereafter is what it is now, there's room for debate on the amount and how it's levied but Apple IS adding value so some compensation makes sense.
But, by offering a first-party service and offering specific advantages not available to competing third-party services does seem anticompetitive. You can't do Spotify on HomePod for example, and Spotify claims they're being restricted with Siri and Apple Watch (I don't know personally, I don't use Spotify or Apple Music myself).
I think Elizabeth Warren might be on the right track: https://www.macrumors.com/2019/03/08/elizabeth-warren-break-up-tech/ - let Apple keep hardware and OS, but any apps should be spun off to independent companies with equal access to App Store.