I get the impression that publishers think only of the short term; so that, when sales responses to a series are good, the publisher orders the mangaka to miiiiiilk the series and, when sales responses are bad, the publisher orders the mangaka to close the series within a very few chapters, or just cancels it outright.
So, yeah, Kumo Desu ga is selling very well, but it is consequently toxically slow. It isn't true that nothing happened in this installment, but nothing worth more than three pages happened.