Hot take: that’s how it should be. After fixing laptops for less technical people, I don’t think the average person can be trusted to protect themselves against malware.
I don't agree there's any links between an appstore and malware.
Sandboxing and app distribution are two concept which might or might not be linked depending on the implementation.
For example, if somebody implemented an appstore for WindowsXP which had zero software protection, the appstore would have been a significant vector of distributing malware as well.
