All of Apple's products this year were just fine. You could settle yourself totally within the Apple ecosystem and use Apple Music and Apple News on your iPhone while taking Live Photos and you would be just fine. You wouldn't have the best time, but you wouldn't have the worst one, either. It would just be fine.
And that's really the issue. We're not used to Apple being just fine. We're used to Apple being wildly better than the competition, or sometimes much worse, but always being ahead of the curve on some significant axis. But what we got in 2015 was an Apple that released more products than ever, all of which felt incomplete in extremely meaningful ways - ways that meant that their products were just fine, and often just the same as everyone else's.
In defense of Apple, the company did put out a significant number of new platforms this year. Let's see if they manage to improve these clearly beta platforms in 2016.