It's not like you can't throw someone into the main event and make it work. Hell, look at Wade Barrett. The nexus invasion was such an intriguing storyline, and he had so much talent/heat, it didn't matter he was a rookie or a kind of generic CAW heel - He looked right at home tangoing with John Cena, Randy Orton, and co. There was nothing uncomfortable about him carrying 10-15 minute opening promo segments to RAW. It was believable that he found himself in a title match at.. survivor series I think it was?
Guys like Wade Barrett, Seth Rollins, Dean Ambrose, Dolph Ziggler, Cody Rhodes, Bray Wyatt, and Cesaro can all be stars if you give them the green light. But instead you have vince giving wrestlemania main events and title matches to part timers from the 90s (Taker, Rock... even Jericho). You have people like Jack Swagger, or The Great Khali, or Roman Reigns, or Ryback, or Curtis Axel get pushed to the moon when they're too dangerous to work with, a few years too green, or just don't have that "it" factor which allows them to carry themselves in the spotlight in a believable manner. You pair your great mouthpieces like Paul Heyman with a guy that doesn't need a mouthpiece (CM Punk) and Brock Lesnar (who's body language, delivery, cocky mannerisms and imposing presence more than make up for any perceived shortcomings he has on the stick as far as wit is concerned... and he's better than people give him credit for), instead of, say, a Dolph Ziggler or a Roman Reigns, who might not be the best at carrying a directionless promo all by themselves, but have the confidence to interject in short bursts and contribute to another person's promo in their own, unique ways.