Synchronizing data across multiple locations or devices is a really hard problem and difficult to get right. There are many variables and determining the single source of truth is often non-trivial. There isn’t even always a right answer.
Understanding that, I have some sympathy for Apple with iCloud (as I do for Google, DropBox and others too.)
But. When you have a service that is being used by billions of consumers, the presence of even small issues or edge cases means that most likely millions of people will have to deal with it.
The good people at TidBITS1 have started a new feature called “Bad Apple” where they talk about annoying and consistent issues folks are having with their Macs. This came about after asking people what problems they were having with their Macs and:
The ensuring conversation spiraled off in numerous directions as various friends and family members griped, kibitzed, and tried to solve each other’s problems. It was fascinating because many of these people were long-time Mac users who had been blindsided by an interface change along the way, and who had thus been frustrated by their Macs ever since.
The first one covers some of the problems with iCloud Photo Library forcing you to re-sync your entire library if you do something apparently harmless like turn it off and back on again.
As I said, these are hard problems often with no easy answers but they need attention. Often this kind of work gets pushed way down the list of priorities in the rush to get new features out the door. Hopefully articles like this will raise the priority internally at Apple.
1 I have been reading TidBITS since the very first issue which I believe I read on one of the comp.mac.* newsgroups. Back in the olden times. (Really. It was 27 years ago.)