Daniels and Rollins are just as vanilla as Reigns is on the mic. The only difference is Daniels and Rollins both came up from the underground scene, so people think they "deserve" to mainevent WM, because they have paid their dues. I'm sorry but that isn't how it works in the WWE.
A certain someone might not agree with this but it has always been about the looks, and it will never change (even once Vince is gone), because when you look at these big guys, kids see a guy you can look up to. Why do you think Cena is shoved down our faces? I'll be the first to admit I'm not the biggest Cena fan, only cause his matches are so damn predictable/boring, and he never puts over talent, but despite that he, is a great role model for kids. The only way Vince f'ked this up, if Reigns turns into another Cena, but until then, I say give Reigns the chance to see what he can do with the title.
Ambrose is a different story, I think he is ready for the spotlight, but how can you give a guy that opportunity, when he just came off a feud, where he loss? His time will come, sooner rather than later.
Ziggler, I can never see him in the world title picture, unless a bunch of injuries occur. He's pretty much the modern day Christian, upper mid-card status.