I honestly don't see what was so horrible about it. It was a promo and it explained why AJ Styles has done what he's done over the last year. What was so bad about it?
Oh, he buried TNA? Was anything that he said inaccurate? CM Punk did the same. Play the excuse that he was a heel at the time if you want, but it was damn obvious that the intention was to turn him face with it.
1) Punk was obviously supposed to turn face, but the fact that he was a heel meant the audience could be shouted at if they weren't reacting the right way. It was a help to Punk, something that AJ missed out on. That's not really AJ or TNA's fault, it just made it harder.
2) CM Punk said that John Cena gets all the breaks and Vince McMahon has his favourites. That is true, but the fact of the matter is, these are really strengths of the WWE masquerading as weaknesses. Oh the biggest star gets pushed. Oh the only man to make hundreds of millions out of wrestling in history has a methodology - these things are both obvious and true and not really weaknesses in the mind of anyone but the sort of people Punk was trying to get through to.
Styles on the other hand was clearly alluding to the fact that WWE has beens came in and didn't succeed in getting over. This is also true, but it is an actual weakness that is highlighted to the audience - "a lot of people you don't care about are featured prominently."
What Punk said was essentially 'I hate the way you run things for your benefit and not mine or my fans'; what Styles said was 'Everything you do turns to shit and I have to sort it out for you'. One presents 'the man' as a powerful adversary, the other presents the man as a lame duck. When you are going for a one man vs. corporate entity angle, you need the latter mentality installed in the fans.
3) His voice and stutter aren't what's important. It was his vocal delivery and body language. The way he spoke lacked any intensity. The way he was pacing around showed that he was affected by what he was saying as if he was afraid of the repercussions. What made the Punk promo better than it was, was Punk's delivery. By sitting down, he showed that he wasn't going to be moved by anyone or by the speech he was saying. AJ was pacing about like someone waiting for the firing squad.
4) AJ attacked the wrong people. Dixie Carter is much more bland and uninteresting than Vince McMahon, that's not AJ's fault, but in light of that he should have gone for Hogan or Bischoff. People have an opinion about them so bringing them up gets them interested. Attacking Mike Tenay should be the least of his concerns.
5) And I think for me, this is the worst thing it did compared to Punk. Punk came out and didn't really say anything that was surprising, but everything he said was true. People were engaged with it because they knew that it was coming from his heart, whether or not he was really saying anything revelatory.
Meanwhile, AJ started by talking about wrestling angles - the thing with Dixie and Christopher Daniels turning his back on him. If you want the audience to buy into a shoot and feel like they're hearing about something really juicy on the inside of the company, you have to present it like that. Talking about some ludicrous affair with Dixie storyline before launching into the 'now this bit is actually real' is plainly not going to get the crowd invested in the reality section of the promo.