Injuries haven't helped, but possibly with the exceptions of Fer and Snodgrass, we don't have players capable of playing him in. It doesn't help that we're poor at retaining possession high up the pitch either, where his exceptional movement can buy him the space needed to create a chance.
I think it's more complicated than that. RvW had his 7 starts at the beginning of the season when new players and a new style of playing were being introduced. He scored one goal and another when Pilks 'brushed' it on the way into the net. Hooper has had 12 games by comparison, and his goals have come in the later games of that. I also watched several of RvW's games at Sporting and thought he played very well with the 4-3-3 they were using. IMO, this is what CH is developing this season, dropping back to a 4-5-1 when the ball is lost, like many European teams do. RvW's toe injury has kept him out of more recent developments in that regard, including more through balls and interplay that were lacking in the early games. My hope is that both RvW and Hooper will be able to benefit from that as the season goes on and City will start picking up points on a regular basis. As for new players, I'd like to see another ACM, with both creativity and goalscoring, another DM with good passing ability as well, and a quality CB or Rb (if Martin becomes the 4th CB).