Throughout the series, the Shinigami have been the focal point. But if you think about it he also took you through Ichigo's past. They fought espada and a bunch of hollows, Ichigo learns about his hollow powers. He lsoses his shinigami and learns about Fullbring (?) capabilities, he infuses that to his normal power and becomes stronger, learns more control. Now he finally gets his soul reaper powers back by learning about his mothers lineage and acknowledging his quincy side, and thus adds on quincy power and gets his real zanpakuto. So following the trend, the last phase of the manga is about the last part of Ichigo, quincies and their history, learning about their strengths, goals, etc. Obviously Johann has to keep killing people to kill time until Ichigo gets there, which I think will be in the room of the Soul King or something.
Kubo: "Oh yeah! I'll just kill everyone and make the quincies the strongest." ... really.. it's starting to be annoying that no one can defeat them. At first I was sad when my favourite character died but now? I don't care... it's just not interesting anymore.. just waiting till Ichigo will die (wouldn't surprise me at all).