The unfinished feeling in iOS 11 mostly comes from UI and animation. UI elements in iOS are quite inconsistent, mixing a variety of UI elements, which might look quite similar but introduce a disconnected feeling for UX. The inconsistency of those elements majorly stems from those UI element updated in iOS 11, such as Large Title and new Search Bar. In my opinion, those newly introduced elements, which might be unfamiliar and new even to Apple engineers, have caused many inconsistent UI experience in iOS 11.
I'm using the public beta of iOS 11.1 on my iPhone and iPad and, as of this writing on Tuesday, October 3, many of these examples are still plaguing iOS 11. Many people won't notice these types of things but as software designers once we see them it is impossible to ignore them.
I'll bet that most of these inconsistencies will take several iterations of iOS 11 to clean up. Meaning, it won't be in this calendar year.