The ingratitude and sense of entitlement that some of these developers have demonstrated is striking. Apple lets you use its IP. It doesn't have to do that. You don't, or shouldn't, have an inherent right to use its IP and you shouldn't act as though you do or should. Apple should be allowed to dictate the terms under which it is willing to let you use its IP just as you should be allowed to dictate the terms under which you are willing to use that IP.
So many of the complaints from these developers amount to this: (Yes, you are helping us, but) we think you should help us more and and in the particular ways we want and, further, we think you should be required to help us more and in the particular ways we want. I put the first part in parenthesis because it's an aspect of the situation that these developers, in their complaints, often seem to not want to acknowledge.
Apple helps these developers, to include its competitors in various markets such as streaming music. It does that in part because it thinks that doing so, at least in the aggregate, helps the iOS ecosystem and those who use it - thus it helps Apple. But some of these developers, to include Apple's competitors, want Apple to have to help them even more. For example, they want Apple to not only allow them to use its IP, but allow them to directly monetize their use of Apple's IP without having to pay Apple a reasonable commission. That in itself is an unreasonable expectation, but in many circumstances Apple allows it. Then they want even more. They want to be able to use Apple's IP to direct customers to an alternate way of paying for their services so that it's even easier for them to directly monetize their use of Apple's IP without having to pay Apple a reasonable commission.
No good deed goes unpunished. That saying isn't, or course, always true. But there's a good deal of truth in it. And its apropos of this situation. Apple is somehow the bad guy because it only helps developers - to include its competitors - in certain ways, it doesn't help them in other ways which they think they are entitled to be helped in.