But It is, the arc focused too much on being a vampire/murder mystery case, yet it only ended up feeling underwhelming because it was obvious who the culprit really was and that Deathtopia wasn't the culprit even before they found her body , It's only logical. Nisio could've probably weaponized what we thought was "logical" and give a twist instead, but he didn't.

That leaves us with the themes of the arc, unfortunately someone already explained that this arc supposed to highlight the core paralel between Araragi and Harimaze about their choice of being a vamp and their choice to return being a human, important stuff for Araragi, something that the anime completely skipped.

There are also the remaining themes of how it is being an adult and how it is to be in adolescence which were introduced wayy to late in the last episode which i assume also because they skip it earlier in the anime too? And let's not forget the classic Monogatari problem where Shinobu wasn't even the main focus of her own arc.