iOS Developer here. First, I want to defend Apple in some regard. Without the App Store, I doubt my app would have ever been as successful as it would have been. While 30% sounds like a big cut, it's standard for software and retail. In addition, it had allowed me to create an app and sell it without worrying about the mess of global taxes, refunds, etc.
However, I feel this notion does fall down in the year 2020 onward. Apps are a great thing, but the system was designed to allow apps to update indefinitely with no other upgrade option. It's sort of assumed that apps are free, or that they will never evolve or change to become more valuable, or that developers were not to be paid for their work to continually update apps to work with Apple's latest changes. This, along with the "no free trial" rule forced us to move into subscriptions to handle the expanding nature of the app. Besides, many apps require services to operate that require ongoing financial support.
While Apple has created in-app subscriptions (mostly by bolting it on to existing IAP systems they built), it has always seemed like a "work in progress". Even today, it's a mess to develop and test. Further, the promotional tools that Apple has offered have always been faulty for us or not aligned with how we actually market the product and even more so for subscriptions. The App Store is also designed to purchase software for individuals and never has taken into account licensing to multiple users for organizations and of course is limited to a single platform, iOS (and Mac but even that has been separated for a long time).
We have moved to a web-based subscription system for our group membership and would never be able to do that through the App Store. It allows us to control our promotions, resale, and retail. We can control and test the experience and provide affiliate revenue to our partners. None of this was ever possible in the App Store with the paltry tools that Apple provides. Simply put, Apple either doesn't understand the needs of developers, or doesn't want to in this regard.
That said, I'm a firm believer that if someone discovers our app in the App Store, that Apple should be the one to take a commission for their work. We continue to sell the app outright and provide a free version unlocked with an IAP subscription. I feel that there is value in that and Apple's lowering of commissions to 15% has been a huge boon for our business. I think that Apple does need to come to grips that software should be able to be sold in other places and perhaps change the App Store to allow their apps to be hosted by Apple, but perhaps not promoted by Apple without some sort of pure monetary system. For instance, your app doesn't appear in searches or in the App Store unless you monetize it through the App Store (and they let Apple promote you) or if you pay commissions.
One last thing... your ranking on the App Store is a combination of your rating, the number of downloads, and the money you make. Period. Let's not kid ourselves, Apple promotes the best performing apps and revenue based on commissions is likely a large part of that equation. Allow that to be handled on the side and your app still appears as normal but influences your ranking.