Apple should not have the power to change the rules as they go. Don't neuter them from enforcing the current rules even if you don't agree with the current rules.
One cannot go without the other. If you can set the rules how ever you want irrespective of your ability to steer the market in your favor, you can also change them as you please in such circumstances.
In effect Apple controls what software can or not be installed, what digital services can or not be installed (i mean literally) in devices that it does not own. In the US context, this means give or take, one in two devices on peoples pockets. That is how the App Store manages to gather 70B in revenue.
Now, some lawyer would probably argue that such thing is not true. Indeed people can install whatever they want on iPhone ... Jail break etc etc. But they fail to mention that such action would be voiding the OS licence, but also voids the warranty of the hardware. So no one would risk doing it while under warranty ... They also fail to mention that Apple can basically refuse to fix, as it does, even simple things has replacing a broken display glass. So indeed, the device and the OS are managed in tandem, meaning they have full control over what can or not be installed on the device and what digital services can be accessed outside the Safari keyhole.
You know my stance well enough as I know yours. I would be inclined to support your stance within the context of a small market share. But the large market share along with the policies give them an incredible ability to siphon the digital market place on top of the devices they sell. That is how they reach 70B revenue with the App Store.
It would be interesting to know the revenue of the Mac App Store in relationship with its macOS device market share and compare that with iOS with relationship their device market share. Through that one would have the idea of the impact in the App Store revenue when faced with a more open market policy. But they don’t provide these metrics, just present the all thing as the App Store revenue.