Lack of competition and tenure prevents WWE from doing this.
Seriously, The WWE is in a very comfortable place right now, they have so much good talent they are just sitting on, they don't feel the need to take risks and outside of New Japan, nobody is even close to competing with them. Why work hard when you can coast and still be #1? In the attitude era, people were hungry and willing to take risks because they had nothing else to lose. Its a publically traded company now, the company itself is going nowhere so no need to stretch outside of the comfort zone.
Also, because there are so many established guys at the top who have been around for a decade plus who are just lingering around, there isn't any room for a hungry younger guy to make a name for himself. Cena and Orton been on top for 13 years and still taking main event spots from talented guys. Its actually why I respect guys like The Rock and Austin because they came in, rode their wave and then moved on to something else. There is only so many spots and the guys on top will always get preferential treatment, but when HHH, Brock, Taker, Kane, Big Show, Cena, Orton AND Batista are all popping up every 4 months, they are all taking spots from guys that could be establishing themselves.