I actually believe that if they allowed side-loading it would be one of the best ways to guarantee that they continue capturing 30% of revenue in perpetuity. This is because they could actually for the first time make developers feel like they're getting something for that 30%, as opposed to it being an "existence tax". Apple could actually with a straight face say "hey, you don't HAVE to be on the store, try doing it on your own". This is much different than the current Hobson's Choice of "you don't have to be on the store, you could just not have an app" which feels increasingly shallow in a duopoly, which gets to another important point: they'd actually have a fantastic argument for regulators: competitors really do have choices other than Apple! It would be very hard to argue that Apple should cater to your app that they don't like when there is another way to deliver that app to all the same customers (that doesn't involve first convincing them to switch platforms).

I honestly believe that some sort of side-loading option would be best for any cynical Apple interests long-term and for developers and for users.

The current course of action just leads to developer frustration (which is fine until a disruptive player enters the market), a super shitty store that leaves customers pissed (with scams, etc.), constant churn in rules to try to appease everyone and kick the can another 2 years (like the 15% reduction), and worst of all, unwanted attention from regulators that could have chaotic effects.