Ronaldo is WC, no doubt. But just like Ronaldo will do better with a CF on the pitch, so would Kulu. Our system benefits too, we need Morata, a CF. Kulu is no CF and Ronaldo is no pure CF either. And they are both roaming and are too far away from each other to combine. I agree Kulu is not a starter yet but he has potential and to me would be better off as a RW/RM but with Morata healthy I can't see Kulu displace Chiesa. So we're forced to put Chiesa on the left. He does well there too but I think he looks a lot more dangerous on the right. For the future we need a LM/LW unless we want to have a bomber/ball winner there in the future too. Although I'd prefer having a playmaker there. So in a way, Kulu could play there but he looks so awkward when he is on the left. In the future I see Kulu as perhaps not a starter but a reliable rotation option to field a bit everywhere as I also think he could be deployed as a mezzela on the right in a midfield trio. What is strange to me, however, is that we don't try to teach Ronaldo and Kulu to stick more together so they can combine. When they are so far away from each other the only way to combine is together with the closest midfielder - hence the backward passes. Another problem is that Dybala and Kulu occupy the same spaces, which is why I think Chiesa fits better.
Finally, Kulu has created chances but the takers have been unable to convert. Yesterday he created at least 2-3 chances and I only saw second half. So the no-end-product-discussion is a bit misleading too. He is creating some, just that we expect more from a starter in Juventus. Give him time though, he will serve a purpose here.