Mania is always fun, what it is not is a booking cycle major moment pinnacle AND fun show and it used to be. Aj vs Shane is proof of what is wrong and people saying "Well Shane will do something insane and stupid so that's enough" are part of the problem, which is their right, but wasting a 39 year old AJ with a likely short list of Mania matches left at this level is the work of morons.
What Vince has lost is the connection that people won't treat your booking seriously if during the largest event of the year you don't turn that booking up to 11 for feuds that matter, you take belts away from full-timers and you don't give people moments that could use them for rub.
That is what is wrong with Mania now and people have been convinced it shouldn't be and never was a long term booking cycle peak or start event. He sort of tried with Goldberg and Lesnar but it required a wheezing geezer that no one believes anymore to try and do it.
He thinks it means ratings and since Mania, by definition exceeds the rest of the year's ratings they claim success under the most obvious red herring argument possible even if it wasn't very good in comparison to other years or overall was just goofy without any payoff.
The artform of wrestling has evolved, he never removed himself as a major heel in his own promotion (I can't stress enough along with Cornette and a few others how this affects how people see his choices) and he doesn't seem to care if the company changes. He'd rather it stay the course and bleed slowly than risk sinking on a sharp turn, but someday his time will end and I think Hunter knows what has to change because NXT is giving him all the evidence he needs.
It is possible to book big events with big names AND make the event market and advertise workrate 5 star matches as a reason to watch wrestling at the same time you just give people enough of both separately as serious and casual matches and book it with the flow and sequence that allows that, The reason people say it doesn't work here is because Vince never tried or at least when he did it was when his roster was thin and the competition for eyes was at maximum and without Stone Cold being the literal embodiment of workrate psychology and booking promo dream, the company dies and possibly all of wrestling is back to territories today.
He and Dunn wanted to make 90210 with wrestling as the vehicle, it's time has come and gone, now is the time for booking and work to synergize and the people will follow if you tell them it's important and make psychology to go with it, which is what it currently lacks. (EG, see most 205 live matches not involving Neville, Aries and a few others that get it.)