I'm not sure why apple can't advertise ios as safe, given the millions of apps in the app store, some small percentage have vulnerability issue. Absolute security is not a destination it's a process. In the same way a 5 start auto rating by NHTSA does not mean no deaths in accidents for that vehicle.Maybe Apple's screeners shoulda woulda coulda, but it's completely fair for Apple to advertise iOS as safest and macOS as most secure vs major competitors. No guarantees ever, they don't claim it, and people don't expect a guarantee.
This problem exists in an order of magnitude greater numbers in Google Play. Your position seems to be that Apple has no right to market its more secure App Store as more secure unless is can guarantee zero exploits. Sure, bad stuff can get through, but if your main concern is the safety of offerings, you'll pick the App Store over Google Play every time. Inversely, Google isn't absolved of dealing with appsec just because they don't advertise it as an asset.
On another note, I'm going to start using LTE more instead of wifi.