Apple still owns the only way for users¹ to install apps in their iphones². Moreover, many small developers will still pay apple to handle their payments³.
¹Regular users, almost all users.
²In the US, where this order applies.
³The sales volume is not enough to justify processing the payment outside the platform.
To be clear, I think that 30% was unreasonable from the start, but 10% would be fine in my book and a fair exchange of value.