I agree it's not his best work but it actually has some pretty good stuff. It's just not as tight as his other books.

It seems that like with Stephen King that the more famous the author gets, the less power the editors get to push back.

In the case of Stephenson, this is counteracted a bit by Stephenson improving his craft somewhat over the years. His earlier novels all had very weak endings in my opinion, and that improved somewhat. But his never novels could use tightening.