Good point. That might probably be the reason why Apple will be able to get away with it in the end. They’re not a monopoly and users do have a choice.
What do you think makes open platforms an issue for mobile phones and not an issue for other devices?
I don't believe this issues you're facing come from android being open, but from google's poor design decisions like granting network access to apps by default.
Apple can do open platforms right if it wanted. It doesn't have to do them poorly like google.
Yes, however in cases like that an app store that only distributes officially signed packages and does some scanning as well as allows community to report issues should handle issues for packages that aren't open source. Nothing stopping something like that from existing if app creators wanted to start using it.
F-droid did wade into the free speech debate in relatively recent history by banning an app. I neither condone nor condemn this action but some people (probably very few given that f-droid itself is rather fringe) were probably put off by it.