What ruins angles in the wrestling business is that they run on for a very extended period of time. Vince looking to capitalize on something has the tendency to not notice when something has run its course or needs to be altered. The Summer of Punk was a great example. First they got Triple H and Kevin Nash involved without knowing if Nash was cleared to wrestle, which led of course to a match between Triple H and CM Punk that no one wanted to see. Then they turn him heel even though he was the most over face in the company, topping Cena merch sales and what not. To top it all off they cant find a credible person for him to drop it to, so by the time his match with Ryback comes around the only other alternative to dropping the belt to a green Ryback is for him to hold onto it. He loses to The Rock in the shittiest way possible, and then they forget to give him a spot in the WM main event, AGAIN. Hes stuck in a rivalry WWE is rushing and will most certainly lose at WM, thats the second match we already know the outcome to for WM 29 (The Rock might also be dropping the belt to film Hercules).
Nexus was the result of WWE giving the members nothing to go on after the stable disbanded. Wade should've won the WWE title during Nexus' height. Otunga and McGuilicutty formed the most uninteresting tag team ever, and Justin Gabriel didnt win any midcard titles despite having more in ring talent than the majority of the midcard.
So as things wind down in these angles WWE management completely struggles with ways of keeping it alive instead of letting it die or taking a big risk (putting the belt on Ryback or Wade).