Rooney was bought for 30m Revan
and played in his preferred position for much of his early career at United. Danny was a youth product who was continually loaned out and then when he did get his chance at United often played out of position on the left.
I actually blame Sir Alex when it comes to our young players. Too many of our young players were played out of position to give them experience. Jones/Smalling are awful RB's, we all know this yet they were played out there rather than at CB. I think it's actually harmed their development not helped and I think it's the same case for Danny.
Last season highlights this with Danny in particular with his drastic change of form when played as a wide forward and when played as a CF. It becomes pretty clear which position he's good at and which position he isn't. 1 win in 10 games as a wide forward... 0 goals scored! You don't need to be an expert in football management to work out that he's rubbish at it.