Yes it's fine but the 30% should be charged to the customer who wants to stay within that ecosystem of course. If they want that white glove treatment they can pay for it. Of course once the users see how much that fluffy ecosystem actually costs them I bet most of them will just pay patreon directly :)

If the platform like patreon is supposed to absorb that fee they will increase prices for everyone even people who won't touch Apple like me. That's not fair. Or more likely, they will just give less to the content creators.

In the EU it's already forbidden to force payments through Apple or to forbid the platforms to charge the fee back to the customer.