Many people have already figured it out.

I would imagine a few years after SwiftUI becomes the primary UI stack used by iOS developers, many of them will be cursing Combine's name, as it will be clear most of the problems making iOS developers' lives difficult will be coming from FRP.

I'm sure the App Store, code signing, and bad dev docs will find a way to retain the lead.

Those are things you have to deal with once in a while, and largely cease to be issues once you get over the learning curve. Bad code is something you have to deal with day in and day out.