The Rock has morphed into a perfectly respectably working Hollywood actor. Will he ever win Oscars, probably not. But he's a solid actor these days, to the point that him showing in films actively makes me excited. Snitch, Gridiron Gang, Pain & Gain, etc show that the guy can act. Also, he's still got natural charisma in spades, which others have already noted.
Also putting him in an action movie plays to his strengths anyway. And if "not being that great an actor" was a career impediment, then Arnold Schwarzenegger wouldn't have been as huge/popular as he was, for as long as he was. Or John Wayne for that matter. The Rock is a better overall actor than both of them I think.