Signal was available on iOS in China until the Chinese government banned Signal.
Apple maintains a curated App Store, which puts them in gatekeeper mode for Chinese laws, in China.
I respect, appreciate, and value a curated App Store. The combination of circumstances above does conflict with my preference for the freedom of Chinese citizens.
But my disagreement is with the Chinese government, and their lack of accountability to the Chinese people. It's ethnocentric of me to assume that the Chinese people want Western-style freedoms -- and some evidence of unknown quality says they generally do not -- but I still believe that there are intrinsic rights of all humans which should not be oppressed by their governments.
I also believe that allowing alternative App Stores, or sideloading, on iOS would be destructive. By being the only game in town, Apple is able to enforce standards that are onerous sometimes (as an iOS developer) and unfairly applied sometimes (because that's a universal truth of the world), but on net add great value to iOS.
You obviously disagree, and that's cool. I'm very glad you are able to choose a product that suits your needs, and I am able to choose a product that suits mine.
Re: macOS App Store. It's different because I treat my phone as an appliance that should not surprise me nor require maintenance. It should always work. All apps should perform a function, and they should be available without extra hassles.
However, I don't hate the idea of additional OS protections on macOS. I like SIP and the ChromeOS RO boot partition model. I would like application segmentation. I use jails on FreeBSD and zones on Solaris.
This is easy for me to appreciate because I have other machines that are tuned to suit other sets of needs. I recognize that people with a single device (phone) or two devices (phone + laptop) who have needs that would conflict with OS restrictions will struggle more than I.