I think it's getting more and more evident they are getting further and further behind.
Compare the amount of patches each version of iOS has gotten throughout the years. Now it to the point where at about the time most people are satisfied with a release (ie iOS 8.4.1) they are releasing another major update.
iOS 8 was the first version of iOS to make it to a X.4 update. iOS 4 had a ton of updates too but there was more of a disconnect between carrier specific phones back then.
iOS has turned into a monster and bringing it all together in a timely manor is getting more and more difficult. This is where you can see good management shine because adding more people can get to the point that it hurts more then it helps and requires ton notch supervisors to bring it all together.
Honestly I wouldn't mind to see more of an El Capitan or snow like approach. Add a couple superficial features and spend the rest of their effort streamlining what is already in place.
iOS 8 had 4 major updates for specific reasons. It had nothing to do with the "state" of the OS.
8.1 was sms continuity and Apple Pay in the US.
8.2 was adding Apple Watch app and support.
8.3 was updates to Unicode. (new emojis)
8.4 was redesigned Music app and Apple Music.
Just because it got to 8.4.1 does not mean it needed that many fixes. They were feature additions and product support.