There are people here that are very jealous of Apple's success. Yet Sony, Microsoft and other charge the same 30%. Go and change their percentage also. Microsoft has estimated that 15% is the breakeven point for Apple. Yes, they do need that much revenue to sustain the App Store, to vet the apps, implement the store mechanism, pay for developer and customer support, implement and support the App Store APIs. Now could they get the same revenue to sustain the App Store? Yes, the could charge you $10,000 for the developer account, charge you for documentation, charge you every time you used one of their APIs, etc. In short, there is no free lunch. If Apple is forced to abandon the agency model they will find a way to charge developers and users to make up the difference.
BTW, people, even me, have been signing up for Netflix and Disney+ and Spotify outside the App Store for many years now. All that Apple have to do is allow the developers to post a link.
Personally, since I don't want my credit card info strewn all over the place, I would let Apple take their pound of flesh.