Everyone has made some valid and solid points in this thread. I'll add some of my opinions on to why there is a loss of interest in wrestling in general.
One thing is the lack of ability to create a proper monster in today's wrestling world. People hate on Brock, but he does bring in business. Why? Because he is a legit and believable bad ass. Back in the 1980s and 1990s, you had guys like the Road Warriors, Demolition, The Undertaker, King Kong Bundy, Big Van Vader, etc, guys you believed were indestructible. WWE did a great job building up Braun, and then he lost his mojo so to speak. The breaking of Kayfabe and the constant bitching on Social Media have turned a lot of fans off to him. Yeah, he is the Universal Champion, but it doesn't have the same impact that it would have had if he had won two or three years ago. Now, you have smaller (And whinier guys) who are main eventing the shows. I know some guys like Rollins, but he does come across as a bitch on Social Media. Will Osprey owned his ass without doing much, and made him look dumb.
I may not agree with Jim Cornette on a lot of things outside of wrestling, but he is spot on, when it comes to things that have killed the business. This wrestling ten year old girls, blow up dolls, and super kicking children has made a once respected past time turn into a legit circus. Making the majority of the matches a car crash hasn't helped neither. A lot of old school fans that left don't want to see a million flips done in a match. They want good technical wrestling. For Christ Sake, WWE had the tag team that was considered the reincarnation of the Brain Busters (although I don't agree with that statement, the jackets don't make you a carbon copy, not one of those guys were as intimidating and serious as Tully and Arn) and could have built around them. Averaging 700K to 900K? Yeah, that's good, except TNA was drawing damn near twice that much on a much cheaper budget back in the day. If there was going to be a serious competitor to go against WWE and bring back the old fans, it would have been TNA from 2002 - 2008. They even dropped that ball. Mainly because Jeff Jarrett couldn't get out of the way of his own ego.