Really I think what killed the CWs was a combination of two things. One, the writing and character work for them was generally terrible.
But most importantly, they didn't stand out. In WCW, the CWs worked because they were completely different from anyone else on the entire show. It was like a different thing entirely. And I think that was the original goal for Triple H with this division, which is why they went with the different colored ropes and different announce teams. But at the end of the day they were forced to work the same WWE style as everyone else, so they just became a segregated group of smaller guys working the same matches as the bigger guys.