Rock/Cena was piff its just that the flaws were VERY flawed.
The one year build made money but it suffered at times because you felt that stalling. If they wanted to wait I think they could have saved the confrontations and announcement till a later date. Let Rock cut his return promo but without the Cena jabs. Have him host and just pop in through the year. Maybe around Survivor Series they start planting the seeds. Cena needs a partner he calls on Rock. Have them team up but be dysfunctional. Have Rock lay out the challenge, Cena accepts and then build for like 5 to 6 months.
So what did happen is that the basis of the 1st feud made zero sense up until like two weeks before the match lol. Cena's mad Rock left without understanding his reasoning, Rock just didn't like Cena. Both guys were super immature and corny at times. All that work shoot stuff they both did. The Wrist notes, calling Rock Dwayne etc it wasn't needed. And it didnt help that Rock was in a lot of ways being villainized for leaving/being an actor by various current wrestlers in the company. Cena, Punk, Orton were all taking jabs. So it felt more like an Actor vs Wrestler, which it was but it didnt need to be that way in the WWE bubble.
All they had to do was build on the legend coming back to take on the current top dog to solidify himself and see if he still had "it" Play to the fact that Cena went on a public tirade for years to goad Rock into coming back. They should have kept it that way and just have Cena respectfully not back down and state his case that hes not going to let a guy who left come in and beat him. Have Rock say you wanted Rock back well now you got him. They waited until two weeks before the match to cut out all the jokes and crap and have them serious about why they wanted to square off. Case in point
Its why I enjoyed the rematch feud more even though the first had a better match. The rematch had better promos and they were way more serious.
Plus, I heard that it was going to be a one off but money was so good they milked it. I think they should have known that coming in. No way a Rock/Cena program wasn't going to be ANYTHING but a success regardless of how we felt about it. You could do a part two without the title and actually have Cena on a downward spiral after his loss. Giving Rock the belt (Plus taking it from Punk) and WWE not following up on a Cena crisis post Mania 28 hurt that rematch aside from the match.