This is not unreasonable. Apps like netfix and spotify can not possibly pay the Apple cut and stay competitive with apples own services which pay nothing.
Not a single user is going to pay 30% extra to listen to the same music.
When you install the app they throw you on a screen that says "You can't continue via the app. Yes, we know it sucks"
They aren't allowed to tell you how to subscribe, they can just say you must and it can't be done in the app. While on Apples own services, it just uses your already filled payment details.
