This is a weird argument. If I got you right, you argue that walled gardens somehow prevent existence of malware.

But it's not walled garden that's doing it, it's sandboxing that does. Apple holds the keys and distributes the revocation lists, so they have a say in what runs on their devices. Walled garden is all about who has a say in this.

The question is - will you personally download a privacy-violating app in that weird manner via a corporate account or something? If yes, then I can see how exactly you personally want a walled garden for yourself. If no then it really sounds like you want Apple ecosystem rather than a walled garden per se.

(I'm intentionally not talking about some Average Joe, as it's hard to argue about hypothetical figures.)