What's holding him down? Well let's see, he botches a lot, has zero character and zero charisma, that's what's holding him down.
In the WWE it doesn't matter how innovative or how many "5 star matches" you have, what matters is how many fans you draw and how loud the ovation is, Shelton just doesn't connect with people.
"Maybe as good as you are likely to in WWE if built properly." Please, explain what "properly" is, because you just saying doesn't say squat, I could say "hornswaggle vs a broom would be epic if booked right" but when they actually do it, I shit all over it and simply say "it wasn't done right" without explaining anything. Explaining after you say that adds to your credibility.
I don't know how you can say he botches a lot, that is complete and utter crap. I have seen him botch maybe a couple of moves in the last 3 months, how does that constitute a reason for him not been pushed, it doesnt. Even if he was botching moves regualarly his pure wrestling ability, and ability to excute well thought out athletic spots means he more than makes up for it. Look at Rey Mysterio he botches in nearly every match he is in. Yet he is main eventing on the smackdown side of things.
Shelton has certainly always lacked a natural ability on the mic, and certainly in todays wrestling enviroment that is a problem. I don't see why they don't just give Shelton a mouthpiece of though in the form of a manager or something, because while he needs to develop his mic skills, telling him to shout "aint no stopping me" aint gonna develop those skills at all.
Shelton has more than enough natural ability to be a sucess though even considering his mic skills. Look at Jericho he has tha package yet he's in no man's land since comming back. Is this Jerichos fault? no. The main problem despite Sheltons flaws regarding mic skills is the fact that the WWE writers have nothing for him.
Simply put Shelton needs a gimmick, look at TNA now people can diss TNA's ability to produce decent storylines, and there poor booking but one thing they do well is gimmick wrestlers. A wrestler who does not have great mic skills needs a good gimmick to help them develop there mic skills if they do not have a manager. Look at Abyss, Eric Young, Gail Kim, Awsome Kong, Tomko, Black Machismo. They all have gimmicks, or something which makes them stand out despite the fact they have no, or poor mic skills. So the alternative to giving shelton a manager would be a gimmick of some sort.
The fact is though WWE have just not given Shelton a sustained push since 2004, I am not talking about beating some jobbers on ECW. I mean a decent push like when he beat HHH in that storyline Shelton was massively over due to HHH been such a heel. WWE messed it up though, they stopped pushing him too early in favour of pushing other talents that had better mic skills. Shelton needs another sustained push, and needs to beat one of the top say 10 stars in WWE to get him to the level he was a few years back. Or at least an intresting feud, because all his past feuds have been boring since the HHH one. But this isnt going to fix the mic skills. SO in my opinion he needs a gimmick,or a manager. I disagree with those who say he's just a spot monkey, but he needs something to liven him up and to give him a way to communicate with the fans. Once he has that given the right push he could still be a top star.