Carlito is talking shit. He is just bitter.
There is one reason why WWE just stopped trying with him. He was brought and pushed hot, and he backed up the push. He was incredibly over in 2005, reaching his high at 2006 when he feuded for the title at New Year's Revolution.
But then, it came the problems. In his feud with Chris Masters entering Backlash, he was the heel, still, he wasn't able to make people boo him, and instead he was cheered as one of the biggest babyfaces. WWE stops for a while and then places him in an important not so midcardish feud with Ric Flair, let's ignore his feud with Randy Orton, in which he failed miserably, in which he got shoot the hell out by Flair, still, he failed to get over out of that feud as a believable face.
History then continues repeating themselves, Carlito just fails to get over as something else than a midcarder. You can't say WWE haven't tried to push him when you see and he has been in feuds with Randy Orton, Triple H, Ric Flair, John Cena, Umaga, was about to feud Bobby Lashley.
The only point he was close to winning the belt in level of overness was 2005-2006, and if made champion it would have been too soon. After then, when WWE tried to add credibility to him by facing in one on one feuds bigger opponents, he failed to go to the next level.
Carlito obviously wants a main event push, but why should he get one? He fails to get over in big feuds, hell, he didn't get over by getting a rub as Vince's lackey and defender against HHH. While I understand Carlito for being mad about his lack of push, why should WWE give him a significative push, if when he gets it, he fails?