Personally for me, as a developer of applications, I could care less about 30% fee. I find it reasonable. What I DO care about is restrictions on owning the device and users' inability to run any app they need - even if it is not vetted by Apple. In part it is because I happen to live in an authoritarian country which government loves to block apps in the AppStore.
And how would said users receive push notifications for their apps from Signal?
UPD: oh boy, and I forgot to mention that such users would also have to buy Macs - you can't build a 'stupid app' for iOS without XCode, which runs only on Macs that support the latest version of macOS.
The right way, of course, is to allow third party appstores and app sideloading. Just like we have it on macOS - and it doesn't look like someone was made unhappy because he can run Steam and buy Sketch directly from the developer.
Someone besides Apple, of course.
Purchasing an iPhone is an act of collective bargaining by consumers against publishers that otherwise would hoover up their private data. "If you don't like it, you can always live like it's 2004, before smart phones" is not an answer iPhone customers accept.