If you aren't using their payment systems you aren't using that specific infrastructure or dev tools though. This isn't about someone wanting Apple's (super nice) payment system for free, it's about Apple forcing them to use it instead of their own solution.

If the antitrust laws were designed to prevent that (they weren't) then there's been a massive failure in enforcement because nothing has changed since Apple launched the App Store in 2008. In reality laws don't require platforms to be "open" or "closed" or dictate how you're supposed to make money. And that kind of regulation would be bad for dynamic markets and competition.

If you look at Spotify's allegations[0], than things did change in 2015 when Apple launched Apple Music, creating a conflict of interest for Apple. Anyhow, anti-trust moves slow. The trust cases against IBM took more than a decade, and the case against Microsoft also took a few years.

[0] https://timetoplayfair.com/timeline/

"Conflict of interest" isn't illegal. Apple has been competing with app developers on their platform from the first days of the App Store. If Spotify is somehow trying to suggest that Apple should be barred from doing so, that's not going to be possible under antitrust laws.

Conflict of interest itself is not illegal, but it does legally restrict Apple from doing some things.

For example, providing private APIs to Apple Music would straight fall under the Microsoft precedent, same for not allowing other apps as default programs. Apple Music would have to use the same store review policies, and Apple may have to separate divisions so AM pays the same store tax (but internally).

> then there's been a massive failure in enforcement

I think basically everyone who works on anti-trust issues would agree that this has indeed been the case. Not just with Apple, but with anti-trust law in general.