If there are alternate app stores, I am sure others would make their apps exclusive there and demand you download them through these stores:
1. Facebook will want a store that allows them to build an app that has no ad or data collection restrictions. 2. Epic will want a store that allows them to directly charge for in-app purchases. 3. Google will want a store that allows them to track your location in the background regardless of your consent. 4. The New York Times will want a store where you cannot find a way to cancel your subscription.
And so on... I end up having to download 5 or 10 stores, and end up with a poor user experience.
And what do I get in return? As a consumer, I see no value for me.
I spend a small fraction of what I spend to buy my iPhone on apps per year. If their developers want to charge more to recoup their 30%, I am fine with that.