Even Vlahovic himself admitted that he is not a top class forward, and that people should not place high hopes on him. He is still playing the same way, a few good matches when he scores, followed by dry spells without goals. That is just the type of striker he is, and there is nothing you can do about it.
Allegri tried to sell him, but his market value was too inflated, so the situation became a stalemate. I am not sure that sacking Allegri was a good idea for Juventus, but the management made that decision. We will see what Allegri can achieve in Milan, but again, I can see that he is not getting proper financial backing for new transfers, so the situation might end up being quite similar.
Vlahovic is a striker, not a forward but he has good free-kick skills and scored many goals from free-kicks. He performed good in Fiorentina and in his first season for Juventus. Later seasons, his performances for Juventus have declined so far and Juventus look to lose their belief on Vlahovic. They also let Moise Kean went away and it's hard to find a top class strikers who are available on transfer market.
In Serie A, there are not too many good strikers and how about bringing Moise Kean back to Turin?