Lukaku's problem is simply this;
Last season he was our main striker. We didn't always play the ball to him but he was the man who's job was to run through the middle, get in the box and score. As any striker should do. It worked to the tune of 15 goals and a fair few match winners. Wonderful stuff.
This season we are playing Naismith as that striker because, in all fairness he has been great for us. So lukaku has to then drop back or go out wide and that doesn't suit his game, or at the very least he has never done that before. If Barkley hadn't got injured then he would be playing up top and probably having a better time of things, but you don't drop a striker in form so in an everton only way, our record signing is being played simply for the sake of it.