1000% this. The App Store is stagnant because Apple refuses to improve their store to where developers choose to distribute their app on the App Store. 30% may have made sense in 2008, but it certainly doesn’t make any sense in 2020.
Imagine if Amazon was the dominant platform, and they were the ones charging an App Store fee, but somehow that included AWS fees as well...
But the developer APIs/processes for dealing with in-app purchases are brutal and virtually unchanged over the past 5 years.