I have difficulty following this argument, especially the "stealing" part. App Store does not just randomly take money from the devs. App Store also provides a service. They do world-wide payment and VAT processing, refund processing, discovery, distribution, user login management, APIs, distributed cloud storage, etc. It costs money to run these things. As a small-time developer, I think this is a great deal for 15%. At the price levels of most small apps it would cost more to use a payment processor + hiring an accountant, not to mention the extra work involved in setting up and maintaining these things. For behemoth like Epic — sure, the "Apple tax" hurts, they'd rather gouge their customers without Apple's involvement. But frankly, I don't see any reason to punish one multi-billion corporation just so other multi-billion corporation can make more money. I care primarily about the interest of the small-time developers.
And this is the point that should be made more often IMO — App Stores (and Apple bing one of the first ones) have democratized software development by making the barrier of entry extremely low. Anyone with some talent or idea can go and write an app, without any additional financial risk. App Store is based around sharing your success. The relatively few successful devs carry the costs to keep that barrier of entry low to everyone. And I really don't want that to change.
On a serious notes, what are the alternatives? What exactly is your argument? That Apple should be charging nothing? Ok, then they also shouldn't be providing any services. You want to do distribution or payment processing? Take care of it yourself. Epic would love this of course, Joe the indie developer instead is dead in the water. Or are you arguing that Apple is charging too much? Well, there are solutions to that as well. They could charge for services individually for example, but that again hurts the small developer, because trying out things starts costing them money.
Frankly, my idea would be to split the App Store into a separate commercial entity and make it nonprofit. I am sympathetic to the argument that the Store itself is not a product but is used to support and create value for Apple's ecosystem. I do think that the devs should pay for running the store, and I like the current success-based model and it's low barrier of entry for new devs, so basing the fees on actual operating costs seems like a good compromise. Of course, similar considerations should apply to other stores as well.