I think it is justified. He came back 2 years ago saying he'd never leave and he was back for good. He promptly left for 8 months to have a shitty tag match. Then he left for another four months and had a shitty match with Cena. He then leaves for another 9 months just to come back to end Punk's record title reign in a mediocre match. He misses 90% of the build for the rematch, which was a decent-good match. He then shows up for 2 weeks to build up the WM main event, where he proceeds to have one of the worst WM main events ever. And this entire thing was just to have Rock give his stamp of approval to Cena so crowds would stop booing him. Then he packs up and goes home with out warning.
The same Cena who has been the number one guy longer than Rock's entire active wrestling career and has more wrestling accolades than Rock.
Worst of all is that he couldn't even be bothered to do Via Satellite shit for anything this year. He'd show up to the PPV, the show before, and maybe after, and that's it. No taped promos, just ads for his movies.
To recap:
Came back in 2011 saying he'd never leave and that he was back for good; Spent over 20 months since then completely off TV.
Since then has had 5 matches. 3 involved Cena, one was above bad (Punk at EC), and one was probably in the top 3-5 worst WM main events ever (WM27, which Rock was also involved in), WM13, WM2000).
Clearly came back to try to recapture the 18-35 male demographic since he was transitioning back into action movies.
Came back just so WWE could piggie back off his popularity and to "pass the torch" to a guy who literally is the most dominant and winningest wrestler in WWE history. There is no higher peak Cena could reach. That whole thing could have been accomplished in one promo of Rock putting Cena over instead of their feud being spread out over 2 years with maybe 2 months worth of build total.
Was picked and totally cool with being the guy to end Punk's record reign, only to not show up to Raw for the next 3 months despite being the champ.
It's really been a shameless cash grab on both sides. So has Brock's return, but they don't try to pretend it isn't in that case. It's even been part of his angles. But they've tried to convince fans that Rock coming back wasn't for money or to promote his movies, but because of his love of wrestling and the people. It's all been a coincidence that he's only shown up for Raw when he had a movie about to come out. It worked and Rock got a lot more buys and ratings. But those same people who bought shows and watched Raw for Rock didn't watch or buy when he wasn't on the show. Worst of all, his come back just made people hate Cena even more (when the idea was fans would accept Cena again if Rock gave his blessing) and tarnished his own legacy.