The problem is that Patreon wouldn't even be able to tell people they can donate to their creators elsewhere due to Apple's assinine anti-steering provisions

This is honestly the main problem I have with that. You can argue that in-app purchase brings convenience etc. etc. and Apple deserves a cut and so on. But this enforced secrecy makes users unaware of the cost - they can't actually decide if the cut is worth the convenience or not. Apple relies on people not knowing the cost of the fees and that feels very dodgy.