Screw the haters. I agree that perhaps he was rushed into the main event too soon, or perhaps shouldn't be a main eventer at all, but some people go way too far with how bad he supposedly is. Sure, he wasn't the best of ring workers at the time, but there has been many WWE champions who have been far worse. His mic skills at the time as a heel were top-tier; one of the best talkers in the company. He produced some gold segments as a mid carder and as a main eventer on the mic.
He's also a company boy who does media better than all the rest, so I can see why WWE wanted to make a star out of him. People hate sometimes for the sake of hating because Miz does have a pretty annoying face, but he's a heel who can get guaranteed heat because of that.