I believe that the problem with writing a light novel series heavily based on witty dialogues is that, after twenty something books, you kinda run out of things to say.
As the anime series is almost a word by word adaptation of the novels, it reflects them by taking forever to just get to the point between endlessly idle chatter and the necessity of reminding the viewer what the story's about every 2 minutes or so like we have some kind of mental disability to grasp what the characters are saying the first ten times they said it, so they have to recap everything again! Even if it isn't as bad as the necessity of the author to remind us what a goddamn vampire is each two paragraphs like in Kizumo, it's still pretty annoying.
At least we were told an excelent story on the Sodachi arcs, which had more relevants moments than the opposite, being, in my view, one of the best narratives of the anime until the moment (it was even weird to watch so many episodes without so much fiddle-faddle), but the second half of the anime could be around 70% shorter and we probably wouldn't miss much by it. Frankly, only the scenes of SurugaxShinobu clash and Senjougahara's call (also other by the very end, which is a bit spoiler-ish) were actually good, because the rest, meh. Not that the story in this arc was useless; it was actually necessary, but it had way too much futile moments when compared to actual narrative development. Even if this particular tale was actually handled in a kinda poor way for such an important event of the story, at least Monogatari still manages to be generally good when it focus on its plot.
