Small developers will likely still use Apple because it is easy. The cut is likely less than the hassle of using a different system.
After an update took away the required login setting for a purchase, Twice I have called Apple and received a refund when my kid spent hundreds of dollars in a couple hours. What is going to happen when that is a malicious game developer? They are not giving that money back. The cable monopolies show how monopolies will make it exceedingly hard to cancel a subscription.
As a mere consumer, that is no longer developing for a living, I do not want this option. I do not really care if companies have to pay Apple a cut. I want easy. I want to trust who has my credit card.