I think these mostly are Google's fault. They chose those Linux libraries and implemented them; they certainly have the resources to modify them, to otherwise secure them, or to develop their own. They are producing an OS not for a laboratory but for the real world where there are OEM components, app ecosystems, and malware. Dealing with those issues is an essential part of what an OS does. If you build a ship that works fine in calm weather but sinks when a storm hits, the problem is not the weather.
But is the cutting edge comparison really that much more skewed in Apple's favor?
I'd say that prior to the improvement on patch cycles as of recent in Android - iOS had an edge, but - outside of the walled garden I'm still very curious on the quality between the two with specific regard to the SDLC and resulting output.
That being said: A lot of Android's security issues are not always Google's fault. Some of them are in generic Linux libraries, some of them are in OEM added components (Samsung), and some of them are security issues unique to an app ecosystem (i.e. on Windows Win32 user applications normally have full permissions as that user, on Android an APK running as a user has a limited set of permissions, if it exceeds those permissions this is now an "exploit" which is now an additional set of security issues), and many are simply malware being placed on an app store.
Android's biggest issue isn't really that it is poorly designed (in particular with SELinux as standard). Android's biggest issue is how horribly the OS update mechanism works, so relatively minor security issues may not be fixed for years.