To be fair, Apple's position in the digital music market predates all of the streaming apps. They may not have gone all in on Apple Music until after Spotify started taking off, but when it came to music, Apple devices were synonymous with them for a very long time.
The problem is they created a marketplace with the App Store, allowed competition in, and for way too long we have all kind of collectively accepted the fact that because it's their platform there allowed to have special privileges over everyone else on it.
With the EU is doing is recognizing that these devices are not niche, they're not game consoles, they are devices that every single person has, and this is a marketplace that every person is active in. It is far too large for Apple to be allowed to have that kind of privilege.
It has nothing to do with what's fair to Apple because regulating capitalism properly should not be about fairness to all parties equally. It should be about balancing the scales and leveling the playing field.