He's had a few, strong moments: he used his belt again despite Micchy saying otherwise and protected the scientists despite his anger at their actions. Otherwise, he's been a completely reactionary character. Micchy or Kaito are usually leading him in a direction, like the Inves catching plan, the Rider Game in Helheim, or the recent assault on Yggdrasil.
I assume that's intentional and it'll change once Kota gets a full understanding of what's going on (when he makes the full symbolic shift from youth to adulthood, probably in the early 30s) but right now it makes him a very passive character. Early Madoka had the same problem.
Kaito is well-defined, my problem with him is that he's far more melodramatic than his *current* origin story lent itself to. I'm just waiting for the other shoe to drop on his lifestory.
Micchy and Takatora are pitch perfect so far, and the rest of Yggdrasil is equally interesting. Bravo and Gridon are tuned a bit too far on the zany side for my taste, but it doesn't detract from my enjoyment of the show.