It's how they're abusing that position which is the problem.

I disagree that they're abusing that position. Hypothetically, Apple could offer only their own first party apps on their app store on Apple devices. They give developers a platform to sell their software that the developers otherwise wouldn't have. That doesn't obligate Apple to allow developers any platform the developers want to have on Apple devices.

It would be different if Apple were the only mobile device manufacturer with the only apps in the world, or if they had an overwhelmingly dominant market position, but they don't. Apple doesn't even make up 20% of the overall mobile device market. Developers would reach a wider market by making apps for Android. The problem isn't that Apple is stifling competition, the problem is that the competition sucks a little bit.