By that same reasoning, should we be concerned about iOS-exclusive apps (ie, Apple Arcade)? Should we be concerned that you need an iPhone to sign up for an Apple credit card? Or that iMessage isn't available on other platforms?

The situation between iOS and Android is very similar to the situation you're scared of with a theoretical 3rd-party app store. Consumers don't have a clean choice between device ownership and a managed device. They also have to consider hardware concerns, network effects, exclusive apps/games and services.

It probably sounds dismissive to you if someone says that you can just choose not to use Facebook or Fortnite if they're not on the official Apple store. In the same way, it's a bit dismissive to say that I can just choose to ignore arguably the only privacy-respecting credit card on the entire market just because I want to use NewPipe on my phone. People often don't get to choose their phone based on one specific design aspect of that phone.

> For better or worse, the App Store being the exclusive way into the iPhone forces third parties to deal.

I do agree with this, and I think this is the heart of the conflict. A lot of people are arguing about whether iOS is a monopoly. That's not really the most important part of this conversation, the important question we should be asking is: "do we want iOS to be a monopoly?"

Being a (semi) monopoly and gatekeeping access to a substantial portion of the mobile market allows Apple to force companies to do certain things. Some people want Apple to have that power, because they think Apple will force companies to be more private and to adapt more consumer-friendly policies. Some people don't want Apple to have that power because they don't trust them with it, they don't trust them not to shut down technologies like game streaming or adblocking.

Apple has used its monopoly power to do some great things with privacy, their stranglehold over browsers on iOS is one of the biggest reasons Chrome hasn't taken over already. But Apple has also hampered the open web and is stalling on PWA features, largely because those features compete with the App Store. They also (imo) almost single-handedly created a low-quality mobile games market by maintaining a strict position for years that games were not artistic statements and by locking serious games out of their platform entirely. Apple's privacy-preserving disposable email system is great, their severe neglect for adblocking is bad. Their requirements around accessibility are extremely helpful, their war against adult content is extremely harmful. It's a situation with both pros and cons.

This debate is not really about whether or not Apple has power over the market, obviously they do. Facebook isn't just dropping iOS after its recent privacy changes. If Apple didn't have any kind of outsized control over the market, then companies wouldn't go along with their changes, they would just support Android instead. If the market allowed it, they would do exactly what you're afraid of with a 3rd-party app store -- they would abandon iOS and only support Android. But they don't, because they can't.

So the debate isn't about what power Apple has, it's really about whether or not Apple should have the power over the market that they obviously do have.