Cast in another light, it was standard Stephenson fare -- the first half of the book explores a topic deeply and interestingly, then the second half basically sets it aside to trail off into some weird no-man's land. Seveneves was particularly obvious version of this issue.
I thought Seveneves was more like two "first half of Stephenson novels" smushed together; I found myself wishing there was more exploration of the "second" world. I thought the cultural evolution stuff was super interesting.