When you look at melee zerg boxing really, is there a lot of rooms for improvement on the execution ? I see we got the execution down pretty well. But it is capped.

and put it into a ratings perspective, I see it capped around 2k ratings. That is NOT bad in any sense. But that is what we have to work with. I can't imagine all those 2200 teams just suddenly forget how to play and let us zerg them down.

I say this from experience. I've played enough melee zerging. When I lose a match to a good team, I ask "is there anything I can improve on ? " and frankly, most of the cases, there is nothing I can think of. I did the best possible. The weakness of melee boxing just cannot be overcome if your opponents know them.