They've all had game time though. He's the only one that has been making things happen.
Because he's the outball for the whole attack, so he sees loads of the ball.
The problem is his conversion rate is abysmal. If he had double the amount of assists, I'd agree with you, but he has four and fewer goals than Gareth Barry despite being our second primary attacker. Lukaku is similar in that his overall performance is often poor, but at least he converts to goals.
All you need is a pair of eyes to see that he's been awful. As we all knew before we signed him, he has one good game in ten. Nowhere near good enough.