The pacing is book 4 is objective fucking shit.
First a time-skip that throws us into an entirely new situation we need lengthy exposition spiels to understand, undermining all the momentum book 3 had been building towards.
Korra is nerfed twice and has to find two different yodas to help her overcome her almost identical idiot issues.
An honest-to-god clip show episode, two thirds of which is Korra and Mako straight up listing the reasons why they suck.
A ham-fisted "romance" that has less meaning to it than the rushed marriage between the two comedy-relief characters.
Plus the Zaofu fight has literally no reason to happen except for Su, Opal and Korra being idiots and the robot is stupid from the get-go.
Giving the other characters shit to do isn't enough of an excuse.
It ends with a giant robot.
Book 4 can suck my anonymous dick. It is shit and giving shit characters more screentime doesn't make up for it.