Whats being asked isn't some massive change to their software. Its freedom for the developer and user to have a choice in payment platforms. As much as Apple tries to obfuscate it, the AppStore is not the kernel, its not the graphics layer, its not the file system, its not something that is needed to run software. The other OS components are already being abstracted away to some extent by cross-platform tooling, and the AppStore is way way easier than those.

On one hand, Apple will never take legal responsibility to audit software on their App Store and certify it free from malware, because doing so will be cost prohibitive and/or impossible. But at the same time, they want to claim its this 'utopia' that will get destroyed if users are allowed the freedom to pick a different store. How about you let us decide that?

Even at much smaller scale, you may need someone more than they need you, and they will negotiate like it - for legal and commercial terms.

Also, terms of service are usually negotiable - presuming you're worth negotiating with. GE has no problem negotiating with Google - you as an individual might have to take what their standard is.