I think you need a reality check.
Yes, iOS is a walled garden. Android on the other hand is a lot more open, and while Google maintains a strong grip on the Google Play app store there are alternatives and its easy to side-load apps. Windows Phone 10 is pretty much the same as Android (you can easily side-load apps) but that as you said Microsoft never really cared much for what happened on the Windows Phone app store.
But lets look at the facts for a moment, which are that the Apple app store generates by far the most revenue for app developers. For example, in Q3/2020 the Apple app store generated $19B revenue, which is almost *double* of what Google generated in the same time with it's Play Store ($10B). And this is despite iPhone's much smaller market share (less than 20% globally, some 48% in the US).
Of that $19B, 70% ($13,.3B) ended up with app developers. Which is still more than what Google Play would pay out even if Google waved it's 30% cut.
On top of that, the Apple app store generated that $19B revenue from just 8.2B downloads while Google's $10B comes from 28.3B downloads (more then 3 times as much as Apple's), which means that Apple customers are a lot more likely to pay for an app while Android users are, for the most part, freeloaders.
All which means that, for developers, it's Apple's model which generates the most revenue.
And yet here you are and argue that it would be much better for developers if the iOS platform was more than the other platforms that earn developers a lot less money or which completely failed in the marketplace. I mean, seriously?
You asked why developers shouldn't have the freedom they had on Windows Phone, but the fact is that the platform went down the drain because it was widely shunned by consumers mostly because Microsoft did not curate its app ecosystem, which was a free for all and resulted in apps that over 99% were either crap (some shitty mobile website packaged as app) or malware (right here on my desk I still have a HP Elite x3 running WP10, I'd say few good apps on WP10 can be counted on one hand while the rest is worthless crap).
You may believe that Microsoft allowing you to implement your own payment system is a good thing. As a customer I can tell you that I think it's horrific. Not only because I don't like the inconvenience to have to enter my credit card details into all the different payment systems app developers want to use, I also don't trust you or any other app developer to implement a payment system in a secure manner in the first place, because many of you have shown to be completely inebt at security. As a customer, I like having a single payment system that the platform operator has its finger on so app devs can't pull any stupid tricks, and I like having a single refund policy from the store operator without having to deal with individual app providers. I also like that the store operator curates the content and keeps the overall quality of apps at a certain level.
As a developer, instead of complaining about "freedum" you should rather spend more time understanding your customers, because there is a reason why the iOS app store is the by far most successful despite iOS having the smaller market share.