If you have a company phone you have a different type of walled garden than even what the iPhone provides through some MDM layer. Apple could offer such a separate MDM-based consumer product and also allow side loading.

Microsoft was forced to open up browsing/programming/AV APIs, on which future innovation was built. What Epic is asking for is no different IMO. I just don't think the benefits of multiple open platforms can be understated similar to Windows vs. Linux over the last twenty years.

Both Linux and Windows represent terrible user experiences for many users. Windows, until recent improvements, had a very rocky relationship with being online (primary attack target for viruses, rootkits, and botnets). The Linux ecosystem's user-hostility to the average computer user is the stuff of legend, although things have obviously improved greatly (this is still not the year that Linux on the desktop gains mainstream acceptance).

I think you've ignored my main point, which is Windows, Linux and MacOS kept innovating by being open and iOS and Android can do the same for phones.

They could, but what's the benefit? Apple is currently innovating by being closed.

(Android is a more complicated story; if you mean "The Android ecosystem tied to Google Play Services and controlled by Google," I can agree. There's a whole chunk of Android not meeting that criteria, and by many people's estimates, it's behind the 'closed' one for features and reliability).

Let's define innovation here, for iOS it would be the A13 and widgets, while for Android it would be folding screens and a modular Android that's easier to update. But you know, this thread is about Fortnite not being on iOS, and Apple weaponizing technologies like Metal and Safari. Apple innovation is lock-in, while Android is not.

If jailbreaking could be done the same way I can unlock the bootloader for my Android device, you would have a point. Unfortunately it requires using security exploits, which Apple is doing its best to plug.