I don't think the 30% has ever been an issue. The exclusivity is. Doubly so as Apple keeps changing the rules which if you're caught on the wrong side of can destroy your business.
Seriously? The 30% on apps, the 30% on in-app purchases, 30% on subscriptions, etc., each caused an uproar when they were announced.
Not to come across as an Apple apologist, but seriously, it wasn't even that frickin' long ago... even in internet time.
Those who do not remember the past are condemned to repeat it, repeatedly, in online forums, but in a badly twisted and inaccurate version.
Apple can destroy your business by changing a rule that makes your app ineligible for the App Store (or at least unprofitable, most recently seen in the whole in-app fiasco). There's not a way to distribute outside of Apple, so if Apple doesn't want to distribute your app then you have no business.