Actually, one of the reasons the Alliance angle was such a failure when it was practically made of gold was for similar reasons to the fact The Rock is getting a bad reception for "stealing a spot". Many of the wrestlers got pissed off thinking that WCW stars were going to stroll in and take the main event spots. Yes, that would've happened with some of them, but WWE have long had a payment system where the wrestlers are paid on a weighted average of the gross of the shows they appeared on, their position on the card, and an estimate of how many paid specifically to see them. Even though they may have had slightly less work, their pay would have actually increased considerably if say, the main event of Survivor Series 2001 featured Sting, Ric Flair, Goldberg, Hulk Hogan and Kevin Nash rather than Shane McMahon and The Big Show.
That said, I believe very little about what is coming out about the feud between John Cena and The Rock, the WWE (particular Jim Ross on Twitter) seem desperate for us to think they legitimately hate each other, and I'm not so sure. I don't even believe the "car crash" is real. The way WWE have been bringing the story up ad nauseum makes me wonder that it's just a desperate attempt to gain Cena some sympathy cheers going into WrestleMania because he's lagging so far behind The Rock in terms of fan support.