Why are you comparing open and closed platforms when they aren’t comparable? Try now with Microsoft Xbox and iOs and your logic fails.

Because the entire definition of "open" and "closed" platforms is an arbitrary one dictated by the platform creator. There is no reason that iOS (and every game console for that matter) can't run arbitrary programs provided by the person who bought and paid for the device other than obstinance in service of rent seeking.

Why should "closed" platforms (i.e. ones where the user doesn't get to decide) even be allowed to exist?

Because the user decided to buy into a closed platform. He could have chosen an open Android platform.

My parents chose iOS over Android for the security, ease of use, unification AND the App Store.

I’d say stop forcing your agenda on the users. They have the right to choose what they want. They voted with their money and do it each year.

Nobody's forcing anything on anyone. What you campaign against with this screed is choice. If someone wants to stay within the walled garden, nobody is taking that from them.

None of that is lost with the ability to have alternative app stores. Creating more choice is the the opposite of forcing anything on users.

It increases the attack vectors for the platform

Maybe, but unlikely. The operating system still needs provide APIs and access. Alternate app stores doesn't mean apps can do anything they want on the device.

I'm not comparing anything, I'm saying closed platforms shouldn't exist. the practical difference is however that the mobile phone is used as a general purpose computer and is at this point for many people the only device they actually use. That said I am not in principle opposed to apply the same standard to gaming consoles, but it is less of a pressing issue compared to the fact that there are hundreds of millions of people with smartphones who basically have no access to any remotely free and open computing environment.