I've been a fan of Ziggler's for a long time and I wouldn't mind seeing him get a big push to the title picture. However, in my opinion, I don't think he's the best in-ring guy on the roster, nor do I see him as being the most charismatic on the roster. As far as his pops go, I've been to a lot of house shows and while he gets strong ones, I've heard others get much stronger.
Look, I know it's fun to play conspiracy theory whenever someone you're a big fan of isn't getting the push you think he deserves but 99% of the time, the theories just don't hold water. As has been pointed out, if there was this big hatred of Ziggler backstage by management, he wouldn't be on television wrestling week in & week out, he wouldn't have spent much of the past year involved in the Intercontinental Championship picture, he wouldn't have competed in the IC title ladder match at WrestleMania, he wouldn't have been in the IC title Elimination Chamber match at the EC ppv this past Sunday, etc.
As others have also mentioned, as of right now, there are guys ahead of Ziggler and it's arguable that they're rightfully ahead of him. Rollins has been an overall entertaining heel champion, Dean Ambrose is hugely over with fans, Roman Reigns is being embraced by the fans at long last, there's still Brock Lesnar waiting in the wings as he has a rematch coming up at some point.
Ziggler has a history of head trauma that has WWE officials concerned. Whenever someone suffers a concussion, WWE officials get understandably very concerned about the wrestler's condition and how to use him/her going forward. In Ziggler's case, he sustained 2 concussions within less than 6 months of each other in 2013 and 2014, plus he came back too soon after suffering the first one and suffered something of a relapse due to Post-concussion syndrome. He'd passed all the various tests, yet about a month after being cleared to compete, the symptoms returned. So, couple that with him legitimately suffering another concussion less than 6 months later, you have a situation that creates doubts as to his fitness in the long run. After all, if he did get the push, even got the belt for that matter, and suffered another concussion, it could throw a monkey-wrench into plans. We saw that happen with Daniel Bryan due to his neck and, let's be honest, he's more over and more popular than Ziggler's ever been; however, if he's able to return, there's a strong possibility that his time as being at the top of the roster is over because of officials fearing that his condition in the long run makes him unreliable. It sucks for Bryan and for Ziggler in my eyes, I'm a fan of both, but it's not as though there's not an abundance of merit if company officials took this particular point of view.