Apple has just engineered the worst possible situation for themselves by being the
only way to get apps on the store and by simultaneously incessantly marketing the store as "Safe and Secure". The former encourages them to maximize the number of apps on the store, while the latter encourages them to shoot first and ask questions later.
If side-loading or alternative ways of getting apps onto the iPhone existed, then they could implement far stricter controls knowing that, worst case scenario, you can still get an app onto the iPhone. This is how it works on the Mac. Tor isn't on the Mac App Store, but that of course doesn't mean Tor can't be used on the Mac.
This is one of the tricky parts about AppStore discussions, it's not about being for or against the AppStore. In fact, I wish the AppStore was MUCH pickier about the apps it let in, and I also wish there was an alternative to the AppStore to catch cases that didn't meet that strict bar. Then the AppStore could actually be about curation as opposed to fear-induced isolationism. Then Apple wouldn't have to inadvertently have political side-effects when it disallowed apps like HKMap.live.
Being on the AppStore could still be advantageous beyond just "either that or you don't get to be on the iPhone at all.” Apple payment processing, iCloud integrations, Family-sharing, etc. could all be tied to being ON the AppStore, so there'd still be a huge incentive to try to ship that way. And side-loading doesn't have to be easy or even on by default.