I mean, isn't the App Store kind of Apple's domain? As unfair as it may seem, Apple kind of built and invested in their App store infrastructure and should be able to leverage all their company's hardwork to generate profit.
You can't take up residence in someone else's home and then demand they also set aside a portion of the house for you to start a business, without additional rent/fees.
Apple will win in the end. Why? Because they've invested in the hardware and its supporting ecosystem. Ultimately, what Spotify has to offer isn't really a unique product. It's just streaming music—a convenience service that Apple can just as easily implement. Google did, Tidal did, Microsoft did, and now YouTube is doing. Don't get mad at Apple because they also have the foundation to support it.