Not enough characterisation or plot or justify the length.

This is Sanderson's attempt at his own sprawling Wheel of Time-style world, which means shallowly touching on a large number of cultures that are each defined by one or two simple attributes. Characterisation has improved since The Final Empire, but like the Wheel of Time there's not enough depth to the characters to justify the amount of time spent on them, and it starts to feel like it's just repeating the same few points about the same characters. While it is a bit less shallow than his previous books, those earlier books were saved by their brisk pace and complex plotting - they were fun quick comic-book-like adventures. There is cooler stuff in here, but it's more of a slog to get from each character or plot point to the next.