This. All of this. As someone who came up watching during the Ruthless Aggression era, early Cena was loved with no objection because the white rapper gimmick people latched onto. However, once he got drafted to Raw and Batista got sent to Smackdown and it became clear WWE chose to have Cena as the new Golden Boy it was over. The fans rejected it, then he had that movie The Marine, and WWE thought that turning him into the ultimate baby face would work out but it didn't. Cena kept going over everybody and the fans kept rejecting him, and he got stale. That was when WWE started their spin of "Well whether you love him or hate him!!!! This crowd is hot, they give a reaction!!!". Cena deserves ultimate credit for being the guy for so long and giving it his all but he was not loved like that at all during the "CENA WINS LOL" era.
But then like you and others said it started to change once he did the US Open Challenge and started to work with the new group of guys coming in. He started to do a lot more in the ring and his promos got a little more edgy. I'd say he's been looked at pretty favorably since then.