There is pretty much a consensus on this forum, and more so on the others, that signing Yates was a costly mistake. But I think that there are reasons for thinking he will be more productive going forwards.
First of all the case for the prosecution. Yates' hold up play is poor, unsurprising given his diminutive size. Secondly he's accused of being pretty invisible. It's certainly true that his game involvement is very limited. Some of this is perhaps down to a lack of movement, but a fair bit will be down to the team's inability to get the ball into the final third and penalty area. Whilst we are near the top of the division for touches in the defensive and middle thirds we are lower half for touches in the attacking third and opposing penalty area. Thirdly, Yates, undeniably, has limited pace over distance.
The case for the defence. His average pass completion is 78.9%, which is at the 95th percentile for forwards. So he clearly can link play, when he gets the ball. Secondly he does work hard out of possession, with his blocks at the 78th percentile for the league. Thirdly, I think he is fairly fast over 10 yards, as could be expected of a smaller player, with lower inertia. This gives him his fox in the box capability.
Going forwards, if the Birmingham game was anything to go by, then Yates can look forwards to more early low crosses across the 6 yard box. This should make proper use of his strengths. There's also reason to think under Williams we will get more possession in the final third and opposing penalty area, which should play more to Yates' strengths in linking play.
My prediction is that between now and the end of the season we will see an improved return from Yates. I doubt he will be hugely prolific, but I think his contribution will be seen in a more positive light by the season's end. To date he's a much a symptom of collective team failure as of his personal limitations.