I enjoy the historical overview, and it does clarify how this fee structure originated (and what it's modeled on).
But to answer your final question, today, I would say that an iPhone is a computer — a mini-supercomputer in your pocket. It has graphics and compute power in excess of many PCs around the planet. We might consider smart phones 'conveniences' or 'appliances', but they are not thin clients, they are full-fledged systems in a tiny, fragile box meant to be mobile and with you at all times.
As much as I dislike Epic Games and Tim Sweeney, and I don't like the idea of an 'open' AppStore, or Apple being unable to control their own platform, I do think that I (and you) should be able to put any software I want on my phone. Just as I can do on my laptop or desktop or tablet (Android e-ink enote tablet!). My iPad is limited in the same way as the phone to 'apps' often forced to be dumbed-down, and worse, censored for 'adult' or non-child content.
Like seriously...I don't need 'Big Bro' Apple looking over my shoulder and warning (nagging) me about content or safety or well, anything. The fact that every single page in the Reddit app pops up a warning of 'unsafe' or 'explicit' content—even when there is none(!) is amazingly horrible as a user experience. Enough so that I avoid the app.
The only galling part of this judgement is that Epic Games is a 'winner' here. Otherwise, I do (now that I have thought about it more) agree with the ruling. Apple should not control our choices, or our ability to discover that there ARE choices. Of course, most of us are capable of finding more information about anything. But the action demanding the least friction will generally be the one people 'choose.'
[edit: fixed "AppStore"]
Good post, I do agree with basically all of it.
Most of the time here i'm just arguing the contrarian view of both sides and how Apple would see it.
If I was totally honest - I do like the idea of easily sideloading apps, though we know through Android that 100% leads to piracy - I bet the app devs complaining about the 15% cut wouldn't be as happen when their sales drop by a ton as everyone just downloaded it for free from a pirate website like you can on macOS
Multiple app-stores would be fine be me just as long as all of the apps are also in the App store so I don't have to manage multiple stores and updates. Though as you say that does leave us under Apple's whim for what content it deems unacceptable.