My main gripe is taking over Zhao has now been way too long, we still have 4/5 states to go so the pace in which Zhao is going down is just way too slow IMO
To be fair, none of the other states have Ri Boku - who has been stated to be #1 obstacle to Qin's ambitions.
Aside from Zhao, only the Chu can viably challenge the Qin, and they've not begun to tap into their full strength.
The other states are all underdogs against Qin, which has become an ascending superstate after all the territory it has conquered. The other states will have their moments, I'm sure, but they won't put as much of a fight as Zhao has and will.