Val Venis?

I've not witnessed him winning a single match on Raw for nearly 5 years. Many years ago he used to win plenty of matches, including title matches. Why does he remain in the undercard level despite having been in the company since the year 1998? Other wrestlers who debuted much later like John Cena, Brock Lesnar, Randy Orton, Shelton Benjamin etc mastered the craft and are now like light miles ahead of him(Cena and Orton are main eventers). Why is that so?