Being more involved in attack doesn't mean you are better in #2 positioning. What i meant was when we are having the possession on the ball, Herrera tends to pass the ball backward without moving around in a better position, as a result we are relying too much on our defenders to build up the attack. You will notice how Herrera involves more in our attack play when he plays a bit further upfield when a player like Carrick who likes to pass forward play deeper.
To put it simple how Kante is better than Herrera is that Kante dominates the game and midfield while Herrera doesn't.