Characters that fans actually want to get behind. Unpredictability (is there anyone here that is doubting Cena and/or Orton will be in every PPV match leading to WM and perhaps beyond). Storylines that are over-the-top yet still entertaining:
Batista/HHH, Edge/Cena, HHH/Orton are the biggest drawing feuds since 2005 and all are lengthy, personal over-the-top prpgrams.
If I'm not mistaken, the viewer numbers are largely the same as they have been for the whole decade, so the answer is nothing. Ratings look weaker because of how many more people own more TVs than back then and just how many TV shows there are now.
What it would take is somehow getting the male 12-35 demographic back. They're into UFC (not MMA, just UFC) right now but changing that is not definitely not impossible. I went to UFC 123 last night and probably 75% of the people don't care about MMA as a sport whatsoever and just wanted to see jacked tough guys talk shit, stand toe to toe and see someone get fucked up. Wrestling COULD provide those things, but it doesn't right now.
Promos are a major problem. 99% of these guys, even ones considered to be good on the mic, are talking like cartoon characters or like they're in an alternate universe, if you want guys 12 and up to get into wrestling you need guy's promos to sound cool or badass. A heel promo should be insulting the opponent aggressively with things a bully would say to someone in real life, not rambling on about titles and doing everything in the business and that kind of thing.
Time machine, Vince McMahon buying a bunch of homes with Neilson box's and tuning into WWE programming on each one, the internet never existing or a show that is directed at all ages not children.
Also a 4.0 in the late 90's early 2000s and a 4.0 in 2010 aren't really comparable. People DVR now, get their media through the internet and have way more options for entertainment than they did back then.