Many stars have screwed up in the ring, hell ECW made that a trademark of their show (You F**ked up chant). Benjamin, like Hardy, attempts many high risk manuevers and once in a while screw up the move (I remember when Jeff fell off the barrier trying his running senton).
MVP is awesome in the ring, but with that ring attire the WWE coulnd't push him if they wanted. Kennedy's push is odd at best. The WWE push him hard then let him fade until pushing him again (Headlining Smackdown and championship shots on PPVs to a minor feud with Lashley back to a push on Smackdown again).
If that is your argument for Nitro, then why the hell did men like Cena (no wrestling ability) and Rey Mysterio (good talent, but not championship material) ever get the belt. And Nitro does not have to win the belt, just consistently contend for it.
Punk has only recently been pushed in any regard. When he first came into ECW he wrestled nobodies and then with matches such as the Elimination Chamber he was misused. And then of course he started losing matches and being booked in nothing matches. The only push he has recieved is getting the MITB match at Wrestlemania.