They aren't even allowing sideloading. They are allowing alternative app stores that they approve, and Apple expects a 27% cut from all app sales after it hits a million downloads.
This means that something like F-Droid on iOS wouldn't be possible due to expense.
Apple isn't going to let you just download an ipa and install it like you can on Android.
You don't own the device you paid for (this could be said about most tech products nowadays)