What else is there to say? They tried to kid themselves into thinking they were giving someone else a chance by having the belt on CM Punk for that long, but they were only cheating themselves. They only really handed over the reigns to Punk shortly after his heel turn, moreso after and in part because of the bone chips in Cena's arm and leg. It's a very good thing, but it's really fucked up the structure of stars in WWE.
IMO, the Cena model serves for bad business and bad entertainment. "Don't put your eggs in one basket", yet there they went.
To be fair, people have often mentioned that inaways WWE were unfortunate to have a) the "lost generation" in Ken Kennedy, MVP, Bobby Lashley etc that were meant to carry the company for a time but never did, and it left the load on the people of Cena's generation and before, and b) that not only did they not get top stars out of the aforementioned people, they also LOST stars, and quite a significant amount from Jeff Hardy in 2009 to Edge in 2011.
Now we're in a super, super weird situation where WWE as we know it can only function because of part timers, and I don't think we've ever been in that situation before.
It seems that at some point in the past 10 year, WWE has drifted from formulas that worked for over 20 years.
-A bad ass is now a funny guy.
-A muscular build is now an average joe build.
-In-ring skills are now more important than charisma.
-Looking tough is now replaced with lookin like a pretty boy.
Why don't they go back to what was successful in the past?
Actually, they do, and I hate it. You see the pushes that Sheamus and Ryback are currently receiving? Tried and tested; as much as we may hate it it's proven to work so that's why they're persisting. Those things you listed are partly to do with the shift to "family friendly entertainment"